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	$111.35	3.833%	$115.618	$115.62	$115.60	$115.60
Purchase #2	$225.75	11.161%	$250.946	$250.95	$250.95	$250.90
Purchase #3	$82.43	4.825%	$86.4072	$86.41	$86.40	$86.40
Purchase #4	$67.39	7.590%	$72.5049	$72.50	$72.50	$72.50
Purchase #5	$51.55	13.865%	$58.6974	$58.70	$58.70	$58.70
Purchase #6	$56.80	4.309%	$59.2475	$59.25	$59.25	$59.20
Purchase #7	$88.67	12.191%	$99.4798	$99.48	$99.50	$99.50
7 purchase totals =	$683.94		$742.9008	$742.91	$742.90	$742.80