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	$106.34	5.468%	$112.1547	$112.15	$112.15	$112.20
Purchase #2	$214.69	13.433%	$243.5293	$243.53	$243.55	$243.50
Purchase #3	$146.86	5.725%	$155.2677	$155.27	$155.25	$155.30
Purchase #4	$245.37	6.587%	$261.5325	$261.53	$261.55	$261.50
Purchase #5	$171.86	9.830%	$188.7538	$188.75	$188.75	$188.80
Purchase #6	$30.62	9.696%	$33.5889	$33.59	$33.60	$33.60
Purchase #7	$222.93	4.768%	$233.5593	$233.56	$233.55	$233.60
7 purchase totals =	$1,138.67		$1,228.3862	$1,228.38	$1,228.40	$1,228.50