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	$161.75	5.662%	$170.9083	$170.91	$170.90	$170.90
Purchase #2	$77.35	11.257%	$86.0573	$86.06	$86.05	$86.10
Purchase #3	$132.41	11.503%	$147.6411	$147.64	$147.65	$147.60
Purchase #4	$58.35	7.742%	$62.8675	$62.87	$62.85	$62.90
Purchase #5	$189.90	5.768%	$200.8534	$200.85	$200.85	$200.90
Purchase #6	$207.42	7.488%	$222.9516	$222.95	$222.95	$223.00
Purchase #7	$124.34	5.478%	$131.1513	$131.15	$131.15	$131.20
7 purchase totals =	$951.52		$1,022.4305	$1,022.43	$1,022.40	$1,022.60