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	$141.52	8.498%	$153.5464	$153.55	$153.55	$153.50
Purchase #2	$37.82	11.231%	$42.0676	$42.07	$42.05	$42.10
Purchase #3	$192.77	12.464%	$216.7969	$216.80	$216.80	$216.80
Purchase #4	$27.28	10.822%	$30.2322	$30.23	$30.25	$30.20
Purchase #5	$156.74	6.239%	$166.519	$166.52	$166.50	$166.50
Purchase #6	$104.61	9.859%	$114.9235	$114.92	$114.90	$114.90
Purchase #7	$210.29	6.299%	$223.5362	$223.54	$223.55	$223.50
7 purchase totals =	$871.03		$947.6218	$947.63	$947.60	$947.50