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	$57.26	3.793%	$59.4319	$59.43	$59.45	$59.40
Purchase #2	$158.48	6.654%	$169.0253	$169.03	$169.05	$169.00
Purchase #3	$236.39	11.700%	$264.0476	$264.05	$264.05	$264.00
Purchase #4	$12.38	4.173%	$12.8966	$12.90	$12.90	$12.90
Purchase #5	$11.93	11.688%	$13.3244	$13.32	$13.30	$13.30
Purchase #6	$10.71	13.514%	$12.1573	$12.16	$12.15	$12.20
Purchase #7	$206.65	8.743%	$224.7174	$224.72	$224.70	$224.70
7 purchase totals =	$693.80		$755.6005	$755.61	$755.60	$755.50