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	$141.34	6.419%	$150.4126	$150.41	$150.40	$150.40
Purchase #2	$71.64	4.301%	$74.7212	$74.72	$74.70	$74.70
Purchase #3	$142.40	11.771%	$159.1619	$159.16	$159.15	$159.20
Purchase #4	$64.27	3.565%	$66.5612	$66.56	$66.55	$66.60
Purchase #5	$232.45	9.117%	$253.6425	$253.64	$253.65	$253.60
Purchase #6	$187.50	4.778%	$196.4588	$196.46	$196.45	$196.50
Purchase #7	$110.35	8.691%	$119.9405	$119.94	$119.95	$119.90
7 purchase totals =	$949.95		$1,020.8987	$1,020.89	$1,020.85	$1,020.90