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	$137.94	9.611%	$151.1974	$151.20	$151.20	$151.20
Purchase #2	$159.79	12.780%	$180.2112	$180.21	$180.20	$180.20
Purchase #3	$126.88	10.463%	$140.1555	$140.16	$140.15	$140.20
Purchase #4	$74.47	3.832%	$77.3237	$77.32	$77.30	$77.30
Purchase #5	$144.58	7.580%	$155.5392	$155.54	$155.55	$155.50
Purchase #6	$133.27	6.470%	$141.8926	$141.89	$141.90	$141.90
Purchase #7	$159.69	5.410%	$168.3292	$168.33	$168.35	$168.30
7 purchase totals =	$936.62		$1,014.6488	$1,014.65	$1,014.65	$1,014.60