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	$202.92	4.429%	$211.9073	$211.91	$211.90	$211.90
Purchase #2	$31.50	7.253%	$33.7847	$33.78	$33.80	$33.80
Purchase #3	$248.72	3.313%	$256.9601	$256.96	$256.95	$257.00
Purchase #4	$102.56	6.291%	$109.012	$109.01	$109.00	$109.00
Purchase #5	$168.55	12.220%	$189.1468	$189.15	$189.15	$189.10
Purchase #6	$10.61	12.133%	$11.8973	$11.90	$11.90	$11.90
Purchase #7	$147.60	4.217%	$153.8243	$153.82	$153.80	$153.80
7 purchase totals =	$912.46		$966.5325	$966.53	$966.50	$966.50