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	$108.64	6.167%	$115.3398	$115.34	$115.35	$115.30
Purchase #2	$237.49	7.770%	$255.943	$255.94	$255.95	$255.90
Purchase #3	$33.37	13.781%	$37.9687	$37.97	$37.95	$38.00
Purchase #4	$151.67	12.192%	$170.1616	$170.16	$170.15	$170.20
Purchase #5	$105.43	3.861%	$109.5007	$109.50	$109.50	$109.50
Purchase #6	$236.42	6.142%	$250.9409	$250.94	$250.95	$250.90
Purchase #7	$107.47	13.336%	$121.8022	$121.80	$121.80	$121.80
7 purchase totals =	$980.49		$1,061.6569	$1,061.65	$1,061.65	$1,061.60