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	$103.26	7.750%	$111.2627	$111.26	$111.25	$111.30
Purchase #2	$66.98	7.409%	$71.9425	$71.94	$71.95	$71.90
Purchase #3	$130.73	5.382%	$137.7659	$137.77	$137.75	$137.80
Purchase #4	$91.54	10.820%	$101.4446	$101.44	$101.45	$101.40
Purchase #5	$35.57	13.554%	$40.3912	$40.39	$40.40	$40.40
Purchase #6	$40.52	13.869%	$46.1397	$46.14	$46.15	$46.10
Purchase #7	$198.90	4.362%	$207.576	$207.58	$207.60	$207.60
7 purchase totals =	$667.50		$716.5226	$716.52	$716.55	$716.50