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	$160.36	6.570%	$170.8957	$170.90	$170.90	$170.90
Purchase #2	$17.34	7.652%	$18.6669	$18.67	$18.65	$18.70
Purchase #3	$195.42	5.142%	$205.4685	$205.47	$205.45	$205.50
Purchase #4	$165.85	7.654%	$178.5442	$178.54	$178.55	$178.50
Purchase #5	$109.29	7.155%	$117.1097	$117.11	$117.10	$117.10
Purchase #6	$86.88	3.423%	$89.8539	$89.85	$89.85	$89.90
Purchase #7	$159.57	7.107%	$170.9106	$170.91	$170.90	$170.90
7 purchase totals =	$894.71		$951.4495	$951.45	$951.40	$951.50