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	$244.42	7.238%	$262.1111	$262.11	$262.10	$262.10
Purchase #2	$154.58	6.442%	$164.538	$164.54	$164.55	$164.50
Purchase #3	$64.76	9.741%	$71.0683	$71.07	$71.05	$71.10
Purchase #4	$148.33	12.371%	$166.6799	$166.68	$166.70	$166.70
Purchase #5	$49.70	12.455%	$55.8901	$55.89	$55.90	$55.90
Purchase #6	$61.67	5.773%	$65.2302	$65.23	$65.25	$65.20
Purchase #7	$180.42	10.696%	$199.7177	$199.72	$199.70	$199.70
7 purchase totals =	$903.88		$985.2353	$985.24	$985.25	$985.20