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	$221.63	13.671%	$251.929	$251.93	$251.95	$251.90
Purchase #2	$85.59	13.258%	$96.9375	$96.94	$96.95	$96.90
Purchase #3	$53.67	10.718%	$59.4224	$59.42	$59.40	$59.40
Purchase #4	$87.40	6.267%	$92.8774	$92.88	$92.90	$92.90
Purchase #5	$20.75	11.352%	$23.1055	$23.11	$23.10	$23.10
Purchase #6	$221.73	10.366%	$244.7145	$244.71	$244.70	$244.70
Purchase #7	$148.79	8.801%	$161.885	$161.89	$161.90	$161.90
7 purchase totals =	$839.56		$930.8713	$930.88	$930.90	$930.80