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	$102.54	3.401%	$106.0274	$106.03	$106.05	$106.00
Purchase #2	$32.55	3.117%	$33.5646	$33.56	$33.55	$33.60
Purchase #3	$125.45	6.381%	$133.455	$133.46	$133.45	$133.50
Purchase #4	$182.57	7.570%	$196.3905	$196.39	$196.40	$196.40
Purchase #5	$218.54	12.212%	$245.2281	$245.23	$245.25	$245.20
Purchase #6	$111.67	8.594%	$121.2669	$121.27	$121.25	$121.30
Purchase #7	$195.88	5.360%	$206.3792	$206.38	$206.40	$206.40
7 purchase totals =	$969.20		$1,042.3117	$1,042.32	$1,042.35	$1,042.40