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	$78.54	13.313%	$88.996	$89.00	$89.00	$89.00
Purchase #2	$53.87	10.838%	$59.7084	$59.71	$59.70	$59.70
Purchase #3	$132.42	7.758%	$142.6931	$142.69	$142.70	$142.70
Purchase #4	$88.41	13.687%	$100.5107	$100.51	$100.50	$100.50
Purchase #5	$134.51	5.813%	$142.3291	$142.33	$142.35	$142.30
Purchase #6	$149.27	5.749%	$157.8515	$157.85	$157.85	$157.90
Purchase #7	$8.88	12.223%	$9.9654	$9.97	$9.95	$10.00
7 purchase totals =	$645.90		$702.0542	$702.06	$702.05	$702.10