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	$155.36	10.738%	$172.0426	$172.04	$172.05	$172.00
Purchase #2	$157.46	4.246%	$164.1458	$164.15	$164.15	$164.10
Purchase #3	$223.89	3.696%	$232.165	$232.17	$232.15	$232.20
Purchase #4	$209.67	5.693%	$221.6065	$221.61	$221.60	$221.60
Purchase #5	$190.78	5.143%	$200.5918	$200.59	$200.60	$200.60
Purchase #6	$30.40	10.176%	$33.4935	$33.49	$33.50	$33.50
Purchase #7	$160.29	7.582%	$172.4432	$172.44	$172.45	$172.40
7 purchase totals =	$1,127.85		$1,196.4884	$1,196.49	$1,196.50	$1,196.40