Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$155.34	12.446%	$174.6736	$174.67	$174.65	$174.70
Purchase #2	$236.76	12.293%	$265.8649	$265.86	$265.85	$265.90
Purchase #3	$178.28	11.520%	$198.8179	$198.82	$198.80	$198.80
Purchase #4	$139.80	13.549%	$158.7415	$158.74	$158.75	$158.70
Purchase #5	$137.28	9.610%	$150.4726	$150.47	$150.45	$150.50
Purchase #6	$205.41	13.151%	$232.4235	$232.42	$232.40	$232.40
Purchase #7	$244.56	11.852%	$273.5453	$273.55	$273.55	$273.50
7 purchase totals =	$1,297.43		$1,454.5393	$1,454.53	$1,454.45	$1,454.50