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	$212.34	13.762%	$241.5622	$241.56	$241.55	$241.60
Purchase #2	$70.54	6.129%	$74.8634	$74.86	$74.85	$74.90
Purchase #3	$13.87	3.231%	$14.3181	$14.32	$14.30	$14.30
Purchase #4	$192.60	7.116%	$206.3054	$206.31	$206.30	$206.30
Purchase #5	$37.77	5.486%	$39.8421	$39.84	$39.85	$39.80
Purchase #6	$104.99	6.308%	$111.6128	$111.61	$111.60	$111.60
Purchase #7	$83.28	7.646%	$89.6476	$89.65	$89.65	$89.60
7 purchase totals =	$715.39		$778.1516	$778.15	$778.10	$778.10