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	$161.59	8.636%	$175.5449	$175.54	$175.55	$175.50
Purchase #2	$36.89	8.728%	$40.1098	$40.11	$40.10	$40.10
Purchase #3	$38.83	3.369%	$40.1382	$40.14	$40.15	$40.10
Purchase #4	$113.25	11.489%	$126.2613	$126.26	$126.25	$126.30
Purchase #5	$91.48	4.831%	$95.8994	$95.90	$95.90	$95.90
Purchase #6	$197.41	13.126%	$223.322	$223.32	$223.30	$223.30
Purchase #7	$128.45	10.301%	$141.6816	$141.68	$141.70	$141.70
7 purchase totals =	$767.90		$842.9572	$842.95	$842.95	$842.90