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	$73.68	11.474%	$82.134	$82.13	$82.15	$82.10
Purchase #2	$210.84	6.217%	$223.9479	$223.95	$223.95	$223.90
Purchase #3	$157.84	3.399%	$163.205	$163.21	$163.20	$163.20
Purchase #4	$33.50	11.138%	$37.2312	$37.23	$37.25	$37.20
Purchase #5	$56.49	5.817%	$59.776	$59.78	$59.80	$59.80
Purchase #6	$98.30	13.557%	$111.6265	$111.63	$111.65	$111.60
Purchase #7	$64.78	12.185%	$72.6734	$72.67	$72.65	$72.70
7 purchase totals =	$695.43		$750.5940	$750.60	$750.65	$750.50