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	$92.69	8.680%	$100.7355	$100.74	$100.75	$100.70
Purchase #2	$33.71	13.518%	$38.2669	$38.27	$38.25	$38.30
Purchase #3	$89.46	6.572%	$95.3393	$95.34	$95.35	$95.30
Purchase #4	$192.79	12.860%	$217.5828	$217.58	$217.60	$217.60
Purchase #5	$25.29	11.107%	$28.099	$28.10	$28.10	$28.10
Purchase #6	$53.76	7.510%	$57.7974	$57.80	$57.80	$57.80
Purchase #7	$141.76	13.366%	$160.7076	$160.71	$160.70	$160.70
7 purchase totals =	$629.46		$698.5285	$698.54	$698.55	$698.50