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	$50.67	11.187%	$56.3385	$56.34	$56.35	$56.30
Purchase #2	$178.51	10.282%	$196.8644	$196.86	$196.85	$196.90
Purchase #3	$221.64	13.462%	$251.4772	$251.48	$251.50	$251.50
Purchase #4	$76.85	10.584%	$84.9838	$84.98	$85.00	$85.00
Purchase #5	$144.62	4.861%	$151.65	$151.65	$151.65	$151.70
Purchase #6	$221.93	7.187%	$237.8801	$237.88	$237.90	$237.90
Purchase #7	$69.33	4.849%	$72.6918	$72.69	$72.70	$72.70
7 purchase totals =	$963.55		$1,051.8858	$1,051.88	$1,051.95	$1,052.00