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	$216.59	12.389%	$243.4233	$243.42	$243.40	$243.40
Purchase #2	$72.67	13.168%	$82.2392	$82.24	$82.25	$82.20
Purchase #3	$101.69	12.683%	$114.5873	$114.59	$114.60	$114.60
Purchase #4	$87.34	6.121%	$92.6861	$92.69	$92.70	$92.70
Purchase #5	$213.76	3.576%	$221.4041	$221.40	$221.40	$221.40
Purchase #6	$147.73	12.737%	$166.5464	$166.55	$166.55	$166.50
Purchase #7	$222.39	3.442%	$230.0447	$230.04	$230.05	$230.00
7 purchase totals =	$1,062.17		$1,150.9311	$1,150.93	$1,150.95	$1,150.80