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	$199.82	13.345%	$226.486	$226.49	$226.50	$226.50
Purchase #2	$195.68	12.702%	$220.5353	$220.54	$220.55	$220.50
Purchase #3	$56.42	3.746%	$58.5335	$58.53	$58.55	$58.50
Purchase #4	$38.46	11.374%	$42.8344	$42.83	$42.85	$42.80
Purchase #5	$185.87	5.277%	$195.6784	$195.68	$195.70	$195.70
Purchase #6	$249.98	10.742%	$276.8329	$276.83	$276.85	$276.80
Purchase #7	$37.49	7.510%	$40.3055	$40.31	$40.30	$40.30
7 purchase totals =	$963.72		$1,061.2060	$1,061.21	$1,061.30	$1,061.10