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	$89.47	7.449%	$96.1346	$96.13	$96.15	$96.10
Purchase #2	$84.67	5.855%	$89.6274	$89.63	$89.65	$89.60
Purchase #3	$30.29	5.775%	$32.0392	$32.04	$32.05	$32.00
Purchase #4	$136.93	6.238%	$145.4717	$145.47	$145.45	$145.50
Purchase #5	$146.66	12.370%	$164.8018	$164.80	$164.80	$164.80
Purchase #6	$54.94	12.292%	$61.6932	$61.69	$61.70	$61.70
Purchase #7	$119.86	3.559%	$124.1258	$124.13	$124.15	$124.10
7 purchase totals =	$662.82		$713.8937	$713.89	$713.95	$713.80