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	$200.47	7.135%	$214.7735	$214.77	$214.75	$214.80
Purchase #2	$123.89	12.301%	$139.1297	$139.13	$139.15	$139.10
Purchase #3	$227.25	4.383%	$237.2104	$237.21	$237.20	$237.20
Purchase #4	$167.90	4.638%	$175.6872	$175.69	$175.70	$175.70
Purchase #5	$125.88	13.219%	$142.5201	$142.52	$142.50	$142.50
Purchase #6	$238.52	9.656%	$261.5515	$261.55	$261.55	$261.60
Purchase #7	$88.51	12.189%	$99.2985	$99.30	$99.30	$99.30
7 purchase totals =	$1,172.42		$1,270.1709	$1,270.17	$1,270.15	$1,270.20