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	$40.50	10.295%	$44.6695	$44.67	$44.65	$44.70
Purchase #2	$33.67	11.365%	$37.4966	$37.50	$37.50	$37.50
Purchase #3	$35.61	13.675%	$40.4797	$40.48	$40.50	$40.50
Purchase #4	$142.41	6.765%	$152.044	$152.04	$152.05	$152.00
Purchase #5	$62.72	5.621%	$66.2455	$66.25	$66.25	$66.20
Purchase #6	$195.81	6.874%	$209.27	$209.27	$209.25	$209.30
Purchase #7	$12.79	6.313%	$13.5974	$13.60	$13.60	$13.60
7 purchase totals =	$523.51		$563.8027	$563.81	$563.80	$563.80