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	$138.56	6.172%	$147.1119	$147.11	$147.10	$147.10
Purchase #2	$67.75	4.481%	$70.7859	$70.79	$70.80	$70.80
Purchase #3	$125.40	13.372%	$142.1685	$142.17	$142.15	$142.20
Purchase #4	$250.44	6.726%	$267.2846	$267.28	$267.30	$267.30
Purchase #5	$238.77	11.231%	$265.5863	$265.59	$265.60	$265.60
Purchase #6	$127.45	12.503%	$143.3851	$143.39	$143.40	$143.40
Purchase #7	$128.62	10.849%	$142.574	$142.57	$142.55	$142.60
7 purchase totals =	$1,076.99		$1,178.8963	$1,178.90	$1,178.90	$1,179.00