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	$99.82	12.831%	$112.6279	$112.63	$112.65	$112.60
Purchase #2	$196.58	13.708%	$223.5272	$223.53	$223.55	$223.50
Purchase #3	$35.99	3.161%	$37.1276	$37.13	$37.15	$37.10
Purchase #4	$14.63	10.188%	$16.1205	$16.12	$16.10	$16.10
Purchase #5	$30.87	3.678%	$32.0054	$32.01	$32.00	$32.00
Purchase #6	$53.56	12.535%	$60.2737	$60.27	$60.25	$60.30
Purchase #7	$169.83	7.516%	$182.5944	$182.59	$182.60	$182.60
7 purchase totals =	$601.28		$664.2767	$664.28	$664.30	$664.20