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	$125.64	4.586%	$131.4019	$131.40	$131.40	$131.40
Purchase #2	$63.39	13.258%	$71.7942	$71.79	$71.80	$71.80
Purchase #3	$197.58	3.368%	$204.2345	$204.23	$204.25	$204.20
Purchase #4	$95.66	5.238%	$100.6707	$100.67	$100.65	$100.70
Purchase #5	$207.73	6.404%	$221.033	$221.03	$221.05	$221.00
Purchase #6	$126.46	12.190%	$141.8755	$141.88	$141.90	$141.90
Purchase #7	$44.78	10.544%	$49.5016	$49.50	$49.50	$49.50
7 purchase totals =	$861.24		$920.5114	$920.50	$920.55	$920.50