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	$89.89	4.848%	$94.2479	$94.25	$94.25	$94.20
Purchase #2	$53.94	9.301%	$58.957	$58.96	$58.95	$59.00
Purchase #3	$136.33	12.730%	$153.6848	$153.68	$153.70	$153.70
Purchase #4	$230.56	3.244%	$238.0394	$238.04	$238.05	$238.00
Purchase #5	$100.83	11.753%	$112.6805	$112.68	$112.70	$112.70
Purchase #6	$172.37	11.236%	$191.7375	$191.74	$191.75	$191.70
Purchase #7	$32.59	3.192%	$33.6303	$33.63	$33.65	$33.60
7 purchase totals =	$816.51		$882.9774	$882.98	$883.05	$882.90