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	$7.59	4.257%	$7.9131	$7.91	$7.90	$7.90
Purchase #2	$81.50	10.814%	$90.3134	$90.31	$90.30	$90.30
Purchase #3	$54.81	7.263%	$58.7909	$58.79	$58.80	$58.80
Purchase #4	$28.43	10.562%	$31.4328	$31.43	$31.45	$31.40
Purchase #5	$209.55	4.623%	$219.2375	$219.24	$219.25	$219.20
Purchase #6	$144.89	6.453%	$154.2398	$154.24	$154.25	$154.20
Purchase #7	$84.75	11.741%	$94.7005	$94.70	$94.70	$94.70
7 purchase totals =	$611.52		$656.6280	$656.62	$656.65	$656.50