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	$154.72	13.301%	$175.2993	$175.30	$175.30	$175.30
Purchase #2	$140.46	5.828%	$148.646	$148.65	$148.65	$148.60
Purchase #3	$186.91	10.332%	$206.2215	$206.22	$206.20	$206.20
Purchase #4	$155.81	8.390%	$168.8825	$168.88	$168.90	$168.90
Purchase #5	$198.82	9.799%	$218.3024	$218.30	$218.30	$218.30
Purchase #6	$210.66	10.859%	$233.5356	$233.54	$233.55	$233.50
Purchase #7	$208.58	7.342%	$223.8939	$223.89	$223.90	$223.90
7 purchase totals =	$1,255.96		$1,374.7812	$1,374.78	$1,374.80	$1,374.70