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	$250.69	4.466%	$261.8858	$261.89	$261.90	$261.90
Purchase #2	$30.34	4.368%	$31.6653	$31.67	$31.65	$31.70
Purchase #3	$158.59	11.851%	$177.3845	$177.38	$177.40	$177.40
Purchase #4	$49.63	11.760%	$55.4665	$55.47	$55.45	$55.50
Purchase #5	$36.68	4.385%	$38.2884	$38.29	$38.30	$38.30
Purchase #6	$233.43	13.341%	$264.5719	$264.57	$264.55	$264.60
Purchase #7	$131.49	12.778%	$148.2918	$148.29	$148.30	$148.30
7 purchase totals =	$890.85		$977.5542	$977.56	$977.55	$977.70