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	$238.55	8.629%	$259.1345	$259.13	$259.15	$259.10
Purchase #2	$63.79	11.174%	$70.9179	$70.92	$70.90	$70.90
Purchase #3	$206.45	11.836%	$230.8854	$230.89	$230.90	$230.90
Purchase #4	$130.47	11.484%	$145.4532	$145.45	$145.45	$145.50
Purchase #5	$190.28	3.393%	$196.7362	$196.74	$196.75	$196.70
Purchase #6	$121.82	4.224%	$126.9657	$126.97	$126.95	$127.00
Purchase #7	$152.95	4.345%	$159.5957	$159.60	$159.60	$159.60
7 purchase totals =	$1,104.31		$1,189.6886	$1,189.70	$1,189.70	$1,189.70