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	$118.26	11.344%	$131.6754	$131.68	$131.70	$131.70
Purchase #2	$48.64	13.418%	$55.1665	$55.17	$55.15	$55.20
Purchase #3	$37.54	8.784%	$40.8375	$40.84	$40.85	$40.80
Purchase #4	$28.85	10.497%	$31.8784	$31.88	$31.90	$31.90
Purchase #5	$210.38	7.359%	$225.8619	$225.86	$225.85	$225.90
Purchase #6	$71.68	9.590%	$78.5541	$78.55	$78.55	$78.60
Purchase #7	$173.36	9.237%	$189.3733	$189.37	$189.35	$189.40
7 purchase totals =	$688.71		$753.3471	$753.35	$753.35	$753.50