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	$82.71	9.478%	$90.5493	$90.55	$90.55	$90.50
Purchase #2	$131.73	9.257%	$143.9242	$143.92	$143.90	$143.90
Purchase #3	$60.50	10.801%	$67.0346	$67.03	$67.05	$67.00
Purchase #4	$122.28	8.345%	$132.4843	$132.48	$132.50	$132.50
Purchase #5	$203.45	9.743%	$223.2721	$223.27	$223.25	$223.30
Purchase #6	$220.73	6.339%	$234.7221	$234.72	$234.70	$234.70
Purchase #7	$120.51	10.695%	$133.3985	$133.40	$133.40	$133.40
7 purchase totals =	$941.91		$1,025.3851	$1,025.37	$1,025.35	$1,025.30