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	$173.43	10.437%	$191.5309	$191.53	$191.55	$191.50
Purchase #2	$244.74	5.607%	$258.4626	$258.46	$258.45	$258.50
Purchase #3	$14.52	10.473%	$16.0407	$16.04	$16.05	$16.00
Purchase #4	$152.53	4.167%	$158.8859	$158.89	$158.90	$158.90
Purchase #5	$76.77	13.252%	$86.9436	$86.94	$86.95	$86.90
Purchase #6	$91.82	7.113%	$98.3512	$98.35	$98.35	$98.40
Purchase #7	$37.98	8.710%	$41.2881	$41.29	$41.30	$41.30
7 purchase totals =	$791.79		$851.5030	$851.50	$851.55	$851.50