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	$227.90	6.586%	$242.9095	$242.91	$242.90	$242.90
Purchase #2	$37.67	7.225%	$40.3917	$40.39	$40.40	$40.40
Purchase #3	$135.58	13.111%	$153.3559	$153.36	$153.35	$153.40
Purchase #4	$7.30	7.548%	$7.851	$7.85	$7.85	$7.90
Purchase #5	$221.84	13.182%	$251.0829	$251.08	$251.10	$251.10
Purchase #6	$233.90	9.797%	$256.8152	$256.82	$256.80	$256.80
Purchase #7	$137.60	8.191%	$148.8708	$148.87	$148.85	$148.90
7 purchase totals =	$1,001.79		$1,101.2770	$1,101.28	$1,101.25	$1,101.40