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	$74.85	13.584%	$85.0176	$85.02	$85.00	$85.00
Purchase #2	$245.49	12.714%	$276.7016	$276.70	$276.70	$276.70
Purchase #3	$95.71	10.416%	$105.6792	$105.68	$105.70	$105.70
Purchase #4	$225.70	12.561%	$254.0502	$254.05	$254.05	$254.10
Purchase #5	$250.83	13.458%	$284.5867	$284.59	$284.60	$284.60
Purchase #6	$104.79	4.342%	$109.34	$109.34	$109.35	$109.30
Purchase #7	$25.65	11.158%	$28.512	$28.51	$28.50	$28.50
7 purchase totals =	$1,023.02		$1,143.8873	$1,143.89	$1,143.90	$1,143.90