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	$179.37	6.132%	$190.369	$190.37	$190.35	$190.40
Purchase #2	$165.58	12.297%	$185.9414	$185.94	$185.95	$185.90
Purchase #3	$118.95	4.353%	$124.1279	$124.13	$124.15	$124.10
Purchase #4	$64.57	9.505%	$70.7074	$70.71	$70.70	$70.70
Purchase #5	$177.78	3.473%	$183.9543	$183.95	$183.95	$184.00
Purchase #6	$68.56	4.322%	$71.5232	$71.52	$71.50	$71.50
Purchase #7	$178.69	9.677%	$195.9818	$195.98	$196.00	$196.00
7 purchase totals =	$953.50		$1,022.6050	$1,022.60	$1,022.60	$1,022.60