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	$57.50	8.659%	$62.4789	$62.48	$62.50	$62.50
Purchase #2	$12.98	6.791%	$13.8615	$13.86	$13.85	$13.90
Purchase #3	$133.72	9.187%	$146.0049	$146.00	$146.00	$146.00
Purchase #4	$140.96	6.842%	$150.6045	$150.60	$150.60	$150.60
Purchase #5	$11.37	4.406%	$11.871	$11.87	$11.85	$11.90
Purchase #6	$94.72	5.263%	$99.7051	$99.71	$99.70	$99.70
Purchase #7	$105.48	10.833%	$116.9066	$116.91	$116.90	$116.90
7 purchase totals =	$556.73		$601.4325	$601.43	$601.40	$601.50