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	$133.77	10.690%	$148.07	$148.07	$148.05	$148.10
Purchase #2	$97.61	12.118%	$109.4384	$109.44	$109.45	$109.40
Purchase #3	$204.36	8.473%	$221.6754	$221.68	$221.70	$221.70
Purchase #4	$87.58	4.514%	$91.5334	$91.53	$91.55	$91.50
Purchase #5	$91.86	8.362%	$99.5413	$99.54	$99.55	$99.50
Purchase #6	$233.53	9.123%	$254.8349	$254.83	$254.85	$254.80
Purchase #7	$37.85	9.364%	$41.3943	$41.39	$41.40	$41.40
7 purchase totals =	$886.56		$966.4877	$966.48	$966.55	$966.40