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	$165.82	13.757%	$188.6319	$188.63	$188.65	$188.60
Purchase #2	$110.90	12.464%	$124.7226	$124.72	$124.70	$124.70
Purchase #3	$152.54	9.225%	$166.6118	$166.61	$166.60	$166.60
Purchase #4	$129.29	9.448%	$141.5053	$141.51	$141.50	$141.50
Purchase #5	$224.91	3.520%	$232.8268	$232.83	$232.85	$232.80
Purchase #6	$44.86	11.671%	$50.0956	$50.10	$50.10	$50.10
Purchase #7	$159.51	8.294%	$172.7398	$172.74	$172.75	$172.70
7 purchase totals =	$987.83		$1,077.1338	$1,077.14	$1,077.15	$1,077.00