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	$248.29	7.278%	$266.3605	$266.36	$266.35	$266.40
Purchase #2	$34.65	8.503%	$37.5963	$37.60	$37.60	$37.60
Purchase #3	$133.26	12.860%	$150.3972	$150.40	$150.40	$150.40
Purchase #4	$185.57	4.469%	$193.8631	$193.86	$193.85	$193.90
Purchase #5	$80.63	11.568%	$89.9573	$89.96	$89.95	$90.00
Purchase #6	$61.68	3.181%	$63.642	$63.64	$63.65	$63.60
Purchase #7	$207.30	10.760%	$229.6055	$229.61	$229.60	$229.60
7 purchase totals =	$951.38		$1,031.4219	$1,031.43	$1,031.40	$1,031.50