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	$36.37	5.710%	$38.4467	$38.45	$38.45	$38.40
Purchase #2	$181.96	7.795%	$196.1438	$196.14	$196.15	$196.10
Purchase #3	$209.98	7.349%	$225.4114	$225.41	$225.40	$225.40
Purchase #4	$111.58	7.205%	$119.6193	$119.62	$119.60	$119.60
Purchase #5	$28.52	5.547%	$30.102	$30.10	$30.10	$30.10
Purchase #6	$40.82	13.778%	$46.4442	$46.44	$46.45	$46.40
Purchase #7	$66.56	7.648%	$71.6505	$71.65	$71.65	$71.70
7 purchase totals =	$675.79		$727.8179	$727.81	$727.80	$727.70