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	$195.86	9.567%	$214.5979	$214.60	$214.60	$214.60
Purchase #2	$209.91	6.578%	$223.7179	$223.72	$223.70	$223.70
Purchase #3	$229.52	10.848%	$254.4183	$254.42	$254.40	$254.40
Purchase #4	$92.33	9.388%	$100.9979	$101.00	$101.00	$101.00
Purchase #5	$215.46	11.412%	$240.0483	$240.05	$240.05	$240.00
Purchase #6	$86.40	4.668%	$90.4332	$90.43	$90.45	$90.40
Purchase #7	$147.52	4.709%	$154.4667	$154.47	$154.45	$154.50
7 purchase totals =	$1,177.00		$1,278.6802	$1,278.69	$1,278.65	$1,278.60