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	$250.25	6.114%	$265.5503	$265.55	$265.55	$265.60
Purchase #2	$18.33	4.139%	$19.0887	$19.09	$19.10	$19.10
Purchase #3	$94.75	11.478%	$105.6254	$105.63	$105.65	$105.60
Purchase #4	$242.53	7.832%	$261.5249	$261.52	$261.50	$261.50
Purchase #5	$52.60	10.782%	$58.2713	$58.27	$58.25	$58.30
Purchase #6	$87.46	13.719%	$99.4586	$99.46	$99.45	$99.50
Purchase #7	$53.69	11.274%	$59.743	$59.74	$59.75	$59.70
7 purchase totals =	$799.61		$869.2622	$869.26	$869.25	$869.30