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	$224.70	3.126%	$231.7241	$231.72	$231.70	$231.70
Purchase #2	$35.98	13.416%	$40.8071	$40.81	$40.80	$40.80
Purchase #3	$223.91	9.654%	$245.5263	$245.53	$245.55	$245.50
Purchase #4	$24.80	5.361%	$26.1295	$26.13	$26.15	$26.10
Purchase #5	$99.80	11.473%	$111.2501	$111.25	$111.25	$111.30
Purchase #6	$209.41	5.821%	$221.5998	$221.60	$221.60	$221.60
Purchase #7	$201.58	3.436%	$208.5063	$208.51	$208.50	$208.50
7 purchase totals =	$1,020.18		$1,085.5432	$1,085.55	$1,085.55	$1,085.50