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	$55.46	6.753%	$59.2052	$59.21	$59.20	$59.20
Purchase #2	$96.91	8.363%	$105.0146	$105.01	$105.00	$105.00
Purchase #3	$76.37	11.372%	$85.0548	$85.05	$85.05	$85.10
Purchase #4	$195.91	5.121%	$205.9426	$205.94	$205.95	$205.90
Purchase #5	$136.51	3.400%	$141.1513	$141.15	$141.15	$141.20
Purchase #6	$57.25	7.757%	$61.6909	$61.69	$61.70	$61.70
Purchase #7	$141.97	11.724%	$158.6146	$158.61	$158.60	$158.60
7 purchase totals =	$760.38		$816.6740	$816.66	$816.65	$816.70