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	$246.67	11.158%	$274.1934	$274.19	$274.20	$274.20
Purchase #2	$94.54	6.103%	$100.3098	$100.31	$100.30	$100.30
Purchase #3	$157.39	7.595%	$169.3438	$169.34	$169.35	$169.30
Purchase #4	$38.56	11.477%	$42.9855	$42.99	$43.00	$43.00
Purchase #5	$203.67	6.554%	$217.0185	$217.02	$217.00	$217.00
Purchase #6	$224.59	5.399%	$236.7156	$236.72	$236.70	$236.70
Purchase #7	$43.80	4.490%	$45.7666	$45.77	$45.75	$45.80
7 purchase totals =	$1,009.22		$1,086.3332	$1,086.34	$1,086.30	$1,086.30