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	$61.45	13.126%	$69.5159	$69.52	$69.50	$69.50
Purchase #2	$119.53	12.458%	$134.421	$134.42	$134.40	$134.40
Purchase #3	$59.25	5.341%	$62.4145	$62.41	$62.40	$62.40
Purchase #4	$233.77	5.502%	$246.632	$246.63	$246.65	$246.60
Purchase #5	$237.30	11.577%	$264.7722	$264.77	$264.75	$264.80
Purchase #6	$131.42	9.854%	$144.3701	$144.37	$144.35	$144.40
Purchase #7	$147.58	12.368%	$165.8327	$165.83	$165.85	$165.80
7 purchase totals =	$990.30		$1,087.9584	$1,087.95	$1,087.90	$1,087.90