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	$124.69	4.757%	$130.6215	$130.62	$130.60	$130.60
Purchase #2	$67.57	11.487%	$75.3318	$75.33	$75.35	$75.30
Purchase #3	$247.50	12.331%	$278.0192	$278.02	$278.00	$278.00
Purchase #4	$131.29	9.572%	$143.8571	$143.86	$143.85	$143.90
Purchase #5	$242.77	5.591%	$256.3433	$256.34	$256.35	$256.30
Purchase #6	$96.41	8.215%	$104.3301	$104.33	$104.35	$104.30
Purchase #7	$61.86	9.693%	$67.8561	$67.86	$67.85	$67.90
7 purchase totals =	$972.09		$1,056.3591	$1,056.36	$1,056.35	$1,056.30