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	$186.75	12.811%	$210.6745	$210.67	$210.65	$210.70
Purchase #2	$233.70	9.480%	$255.8548	$255.85	$255.85	$255.90
Purchase #3	$149.97	12.445%	$168.6338	$168.63	$168.65	$168.60
Purchase #4	$82.52	12.403%	$92.755	$92.76	$92.75	$92.80
Purchase #5	$78.34	10.718%	$86.7365	$86.74	$86.75	$86.70
Purchase #6	$120.72	5.678%	$127.5745	$127.57	$127.55	$127.60
Purchase #7	$12.31	7.160%	$13.1914	$13.19	$13.20	$13.20
7 purchase totals =	$864.31		$955.4205	$955.41	$955.40	$955.50