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	$136.64	10.599%	$151.1225	$151.12	$151.10	$151.10
Purchase #2	$161.77	10.147%	$178.1848	$178.18	$178.20	$178.20
Purchase #3	$125.62	4.161%	$130.847	$130.85	$130.85	$130.80
Purchase #4	$190.31	5.474%	$200.7276	$200.73	$200.75	$200.70
Purchase #5	$161.60	5.607%	$170.6609	$170.66	$170.65	$170.70
Purchase #6	$72.59	5.548%	$76.6173	$76.62	$76.60	$76.60
Purchase #7	$190.45	6.731%	$203.2692	$203.27	$203.25	$203.30
7 purchase totals =	$1,038.98		$1,111.4293	$1,111.43	$1,111.40	$1,111.40