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	$227.61	6.124%	$241.5488	$241.55	$241.55	$241.50
Purchase #2	$53.86	6.533%	$57.3787	$57.38	$57.40	$57.40
Purchase #3	$229.61	9.604%	$251.6617	$251.66	$251.65	$251.70
Purchase #4	$108.30	13.777%	$123.2205	$123.22	$123.20	$123.20
Purchase #5	$222.47	13.837%	$253.2532	$253.25	$253.25	$253.30
Purchase #6	$38.82	3.503%	$40.1799	$40.18	$40.20	$40.20
Purchase #7	$171.48	7.545%	$184.4182	$184.42	$184.40	$184.40
7 purchase totals =	$1,052.15		$1,151.6610	$1,151.66	$1,151.65	$1,151.70