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	$60.91	3.282%	$62.9091	$62.91	$62.90	$62.90
Purchase #2	$186.71	5.224%	$196.4637	$196.46	$196.45	$196.50
Purchase #3	$93.59	6.778%	$99.9335	$99.93	$99.95	$99.90
Purchase #4	$232.65	5.133%	$244.5919	$244.59	$244.60	$244.60
Purchase #5	$53.99	13.283%	$61.1615	$61.16	$61.15	$61.20
Purchase #6	$19.30	3.665%	$20.0073	$20.01	$20.00	$20.00
Purchase #7	$24.26	9.302%	$26.5167	$26.52	$26.50	$26.50
7 purchase totals =	$671.41		$711.5837	$711.58	$711.55	$711.60