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	$229.91	12.395%	$258.4073	$258.41	$258.40	$258.40
Purchase #2	$127.69	3.318%	$131.9268	$131.93	$131.95	$131.90
Purchase #3	$188.60	5.675%	$199.3031	$199.30	$199.30	$199.30
Purchase #4	$199.47	5.837%	$211.1131	$211.11	$211.10	$211.10
Purchase #5	$31.41	12.162%	$35.2301	$35.23	$35.25	$35.20
Purchase #6	$167.70	3.646%	$173.8143	$173.81	$173.80	$173.80
Purchase #7	$67.54	7.207%	$72.4076	$72.41	$72.40	$72.40
7 purchase totals =	$1,012.32		$1,082.2023	$1,082.20	$1,082.20	$1,082.10