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	$44.28	11.305%	$49.2859	$49.29	$49.30	$49.30
Purchase #2	$225.54	8.154%	$243.9305	$243.93	$243.95	$243.90
Purchase #3	$205.86	11.194%	$228.904	$228.90	$228.90	$228.90
Purchase #4	$180.53	6.125%	$191.5875	$191.59	$191.60	$191.60
Purchase #5	$136.37	10.478%	$150.6588	$150.66	$150.65	$150.70
Purchase #6	$48.82	11.268%	$54.321	$54.32	$54.30	$54.30
Purchase #7	$98.60	7.207%	$105.7061	$105.71	$105.70	$105.70
7 purchase totals =	$940.00		$1,024.3938	$1,024.40	$1,024.40	$1,024.40