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	$107.83	3.284%	$111.3711	$111.37	$111.35	$111.40
Purchase #2	$156.93	7.787%	$169.1501	$169.15	$169.15	$169.20
Purchase #3	$221.33	11.246%	$246.2208	$246.22	$246.20	$246.20
Purchase #4	$205.68	10.862%	$228.021	$228.02	$228.00	$228.00
Purchase #5	$202.56	12.632%	$228.1474	$228.15	$228.15	$228.10
Purchase #6	$42.45	12.424%	$47.724	$47.72	$47.70	$47.70
Purchase #7	$105.34	13.766%	$119.8411	$119.84	$119.85	$119.80
7 purchase totals =	$1,042.12		$1,150.4755	$1,150.47	$1,150.40	$1,150.40