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	$115.33	8.717%	$125.3833	$125.38	$125.40	$125.40
Purchase #2	$34.71	5.462%	$36.6059	$36.61	$36.60	$36.60
Purchase #3	$101.27	10.314%	$111.715	$111.72	$111.70	$111.70
Purchase #4	$152.49	5.513%	$160.8968	$160.90	$160.90	$160.90
Purchase #5	$194.72	12.117%	$218.3142	$218.31	$218.30	$218.30
Purchase #6	$178.33	6.511%	$189.9411	$189.94	$189.95	$189.90
Purchase #7	$199.68	9.321%	$218.2922	$218.29	$218.30	$218.30
7 purchase totals =	$976.53		$1,061.1485	$1,061.15	$1,061.15	$1,061.10