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	$36.83	12.122%	$41.2945	$41.29	$41.30	$41.30
Purchase #2	$59.45	4.237%	$61.9689	$61.97	$61.95	$62.00
Purchase #3	$196.25	11.322%	$218.4694	$218.47	$218.45	$218.50
Purchase #4	$161.42	3.815%	$167.5782	$167.58	$167.60	$167.60
Purchase #5	$58.34	7.576%	$62.7598	$62.76	$62.75	$62.80
Purchase #6	$80.57	5.390%	$84.9127	$84.91	$84.90	$84.90
Purchase #7	$61.48	6.385%	$65.4055	$65.41	$65.40	$65.40
7 purchase totals =	$654.34		$702.3890	$702.39	$702.35	$702.50