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	$179.69	13.113%	$203.2527	$203.25	$203.25	$203.30
Purchase #2	$124.61	13.639%	$141.6056	$141.61	$141.60	$141.60
Purchase #3	$248.72	11.727%	$277.8874	$277.89	$277.90	$277.90
Purchase #4	$126.91	8.497%	$137.6935	$137.69	$137.70	$137.70
Purchase #5	$196.66	7.681%	$211.7655	$211.77	$211.75	$211.80
Purchase #6	$52.79	11.205%	$58.7051	$58.71	$58.70	$58.70
Purchase #7	$52.76	5.365%	$55.5906	$55.59	$55.60	$55.60
7 purchase totals =	$982.14		$1,086.5004	$1,086.51	$1,086.50	$1,086.60