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	$208.77	7.406%	$224.2315	$224.23	$224.25	$224.20
Purchase #2	$236.37	12.475%	$265.8572	$265.86	$265.85	$265.90
Purchase #3	$189.73	9.869%	$208.4545	$208.45	$208.45	$208.50
Purchase #4	$151.40	10.659%	$167.5377	$167.54	$167.55	$167.50
Purchase #5	$189.70	10.539%	$209.6925	$209.69	$209.70	$209.70
Purchase #6	$55.58	5.760%	$58.7814	$58.78	$58.80	$58.80
Purchase #7	$36.52	4.744%	$38.2525	$38.25	$38.25	$38.30
7 purchase totals =	$1,068.07		$1,172.8073	$1,172.80	$1,172.85	$1,172.90