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	$47.72	10.840%	$52.8928	$52.89	$52.90	$52.90
Purchase #2	$238.88	8.545%	$259.2923	$259.29	$259.30	$259.30
Purchase #3	$28.54	6.753%	$30.4673	$30.47	$30.45	$30.50
Purchase #4	$12.61	12.213%	$14.1501	$14.15	$14.15	$14.20
Purchase #5	$182.29	5.671%	$192.6277	$192.63	$192.65	$192.60
Purchase #6	$243.89	11.749%	$272.5446	$272.54	$272.55	$272.50
Purchase #7	$37.54	7.274%	$40.2707	$40.27	$40.25	$40.30
7 purchase totals =	$791.47		$862.2455	$862.24	$862.25	$862.30