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	$154.78	7.598%	$166.5402	$166.54	$166.55	$166.50
Purchase #2	$209.47	4.309%	$218.4961	$218.50	$218.50	$218.50
Purchase #3	$233.83	9.520%	$256.0906	$256.09	$256.10	$256.10
Purchase #4	$109.73	13.858%	$124.9364	$124.94	$124.95	$124.90
Purchase #5	$173.53	8.645%	$188.5317	$188.53	$188.55	$188.50
Purchase #6	$113.70	12.489%	$127.9	$127.90	$127.90	$127.90
Purchase #7	$213.55	13.777%	$242.9708	$242.97	$242.95	$243.00
7 purchase totals =	$1,208.59		$1,325.4658	$1,325.47	$1,325.50	$1,325.40