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	$243.95	12.526%	$274.5072	$274.51	$274.50	$274.50
Purchase #2	$244.64	11.225%	$272.1008	$272.10	$272.10	$272.10
Purchase #3	$119.38	9.668%	$130.9217	$130.92	$130.90	$130.90
Purchase #4	$232.40	9.750%	$255.059	$255.06	$255.05	$255.10
Purchase #5	$210.72	13.231%	$238.6004	$238.60	$238.60	$238.60
Purchase #6	$83.48	7.497%	$89.7385	$89.74	$89.75	$89.70
Purchase #7	$240.67	12.768%	$271.3987	$271.40	$271.40	$271.40
7 purchase totals =	$1,375.24		$1,532.3263	$1,532.33	$1,532.30	$1,532.30