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	$188.35	11.242%	$209.5243	$209.52	$209.50	$209.50
Purchase #2	$38.58	3.868%	$40.0723	$40.07	$40.05	$40.10
Purchase #3	$20.29	4.200%	$21.1422	$21.14	$21.15	$21.10
Purchase #4	$218.25	3.398%	$225.6661	$225.67	$225.65	$225.70
Purchase #5	$57.74	3.432%	$59.7216	$59.72	$59.70	$59.70
Purchase #6	$101.90	13.245%	$115.3967	$115.40	$115.40	$115.40
Purchase #7	$85.37	5.362%	$89.9475	$89.95	$89.95	$89.90
7 purchase totals =	$710.48		$761.4707	$761.47	$761.40	$761.40