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	$107.93	3.769%	$111.9979	$112.00	$112.00	$112.00
Purchase #2	$18.29	10.553%	$20.2201	$20.22	$20.20	$20.20
Purchase #3	$148.77	11.146%	$165.3519	$165.35	$165.35	$165.40
Purchase #4	$126.70	12.500%	$142.5375	$142.54	$142.55	$142.50
Purchase #5	$216.54	5.812%	$229.1253	$229.13	$229.15	$229.10
Purchase #6	$47.94	9.591%	$52.5379	$52.54	$52.55	$52.50
Purchase #7	$181.42	3.367%	$187.5284	$187.53	$187.55	$187.50
7 purchase totals =	$847.59		$909.2990	$909.31	$909.35	$909.20