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	$215.86	5.758%	$228.2892	$228.29	$228.30	$228.30
Purchase #2	$78.39	7.723%	$84.4441	$84.44	$84.45	$84.40
Purchase #3	$52.33	4.724%	$54.8021	$54.80	$54.80	$54.80
Purchase #4	$210.61	5.593%	$222.3894	$222.39	$222.40	$222.40
Purchase #5	$116.47	11.193%	$129.5065	$129.51	$129.50	$129.50
Purchase #6	$33.34	11.635%	$37.2191	$37.22	$37.20	$37.20
Purchase #7	$131.42	11.222%	$146.168	$146.17	$146.15	$146.20
7 purchase totals =	$838.42		$902.8184	$902.82	$902.80	$902.80