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	$174.30	12.787%	$196.5877	$196.59	$196.60	$196.60
Purchase #2	$55.30	6.474%	$58.8801	$58.88	$58.90	$58.90
Purchase #3	$195.78	9.380%	$214.1442	$214.14	$214.15	$214.10
Purchase #4	$172.80	4.576%	$180.7073	$180.71	$180.70	$180.70
Purchase #5	$23.49	9.189%	$25.6485	$25.65	$25.65	$25.60
Purchase #6	$93.48	12.500%	$105.165	$105.17	$105.15	$105.20
Purchase #7	$111.42	13.421%	$126.3737	$126.37	$126.35	$126.40
7 purchase totals =	$826.57		$907.5065	$907.51	$907.50	$907.50