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	$116.54	4.305%	$121.557	$121.56	$121.55	$121.60
Purchase #2	$213.37	7.255%	$228.85	$228.85	$228.85	$228.90
Purchase #3	$25.48	12.534%	$28.6737	$28.67	$28.65	$28.70
Purchase #4	$171.25	12.190%	$192.1254	$192.13	$192.15	$192.10
Purchase #5	$37.71	9.414%	$41.26	$41.26	$41.25	$41.30
Purchase #6	$206.28	8.357%	$223.5188	$223.52	$223.50	$223.50
Purchase #7	$207.61	8.518%	$225.2942	$225.29	$225.30	$225.30
7 purchase totals =	$978.24		$1,061.2791	$1,061.28	$1,061.25	$1,061.40