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	$89.34	13.253%	$101.1802	$101.18	$101.20	$101.20
Purchase #2	$73.28	3.204%	$75.6279	$75.63	$75.65	$75.60
Purchase #3	$70.90	10.668%	$78.4636	$78.46	$78.45	$78.50
Purchase #4	$46.25	8.193%	$50.0393	$50.04	$50.05	$50.00
Purchase #5	$151.85	5.639%	$160.4128	$160.41	$160.40	$160.40
Purchase #6	$154.25	9.384%	$168.7248	$168.72	$168.70	$168.70
Purchase #7	$96.59	7.618%	$103.9482	$103.95	$103.95	$103.90
7 purchase totals =	$682.46		$738.3968	$738.39	$738.40	$738.30