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	$223.70	11.690%	$249.8505	$249.85	$249.85	$249.90
Purchase #2	$26.35	6.696%	$28.1144	$28.11	$28.10	$28.10
Purchase #3	$247.81	3.269%	$255.9109	$255.91	$255.90	$255.90
Purchase #4	$157.28	3.425%	$162.6668	$162.67	$162.65	$162.70
Purchase #5	$133.88	13.462%	$151.9029	$151.90	$151.90	$151.90
Purchase #6	$101.71	3.307%	$105.0735	$105.07	$105.05	$105.10
Purchase #7	$76.67	9.297%	$83.798	$83.80	$83.80	$83.80
7 purchase totals =	$967.40		$1,037.3170	$1,037.31	$1,037.25	$1,037.40