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	$194.45	7.654%	$209.3332	$209.33	$209.35	$209.30
Purchase #2	$57.78	7.776%	$62.273	$62.27	$62.25	$62.30
Purchase #3	$238.31	7.545%	$256.2905	$256.29	$256.30	$256.30
Purchase #4	$98.41	7.208%	$105.5034	$105.50	$105.50	$105.50
Purchase #5	$66.53	12.199%	$74.646	$74.65	$74.65	$74.60
Purchase #6	$158.84	13.307%	$179.9768	$179.98	$180.00	$180.00
Purchase #7	$24.56	11.793%	$27.4564	$27.46	$27.45	$27.50
7 purchase totals =	$838.88		$915.4793	$915.48	$915.50	$915.50