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	$227.46	4.485%	$237.6616	$237.66	$237.65	$237.70
Purchase #2	$123.81	11.169%	$137.6383	$137.64	$137.65	$137.60
Purchase #3	$225.78	11.130%	$250.9093	$250.91	$250.90	$250.90
Purchase #4	$173.36	12.784%	$195.5223	$195.52	$195.50	$195.50
Purchase #5	$51.83	11.724%	$57.9065	$57.91	$57.90	$57.90
Purchase #6	$55.43	7.377%	$59.5191	$59.52	$59.50	$59.50
Purchase #7	$168.89	3.660%	$175.0714	$175.07	$175.05	$175.10
7 purchase totals =	$1,026.56		$1,114.2285	$1,114.23	$1,114.15	$1,114.20