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	$84.66	13.635%	$96.2034	$96.20	$96.20	$96.20
Purchase #2	$39.28	4.103%	$40.8917	$40.89	$40.90	$40.90
Purchase #3	$40.67	12.658%	$45.818	$45.82	$45.80	$45.80
Purchase #4	$213.94	11.319%	$238.1559	$238.16	$238.15	$238.20
Purchase #5	$181.91	9.654%	$199.4716	$199.47	$199.45	$199.50
Purchase #6	$223.59	6.536%	$238.2038	$238.20	$238.20	$238.20
Purchase #7	$23.90	11.782%	$26.7159	$26.72	$26.70	$26.70
7 purchase totals =	$807.95		$885.4603	$885.46	$885.40	$885.50