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	$71.28	11.250%	$79.299	$79.30	$79.30	$79.30
Purchase #2	$18.90	8.287%	$20.4662	$20.47	$20.45	$20.50
Purchase #3	$50.35	5.313%	$53.0251	$53.03	$53.05	$53.00
Purchase #4	$58.75	4.798%	$61.5688	$61.57	$61.55	$61.60
Purchase #5	$108.95	13.719%	$123.8969	$123.90	$123.90	$123.90
Purchase #6	$39.39	9.197%	$43.0127	$43.01	$43.00	$43.00
Purchase #7	$18.98	3.653%	$19.6733	$19.67	$19.65	$19.70
7 purchase totals =	$366.60		$400.9420	$400.95	$400.90	$401.00