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	$122.47	3.742%	$127.0528	$127.05	$127.05	$127.10
Purchase #2	$68.72	4.377%	$71.7279	$71.73	$71.75	$71.70
Purchase #3	$21.86	9.305%	$23.8941	$23.89	$23.90	$23.90
Purchase #4	$188.82	7.661%	$203.2855	$203.29	$203.30	$203.30
Purchase #5	$65.67	13.723%	$74.6819	$74.68	$74.70	$74.70
Purchase #6	$174.46	12.856%	$196.8886	$196.89	$196.90	$196.90
Purchase #7	$200.59	8.170%	$216.9782	$216.98	$217.00	$217.00
7 purchase totals =	$842.59		$914.5090	$914.51	$914.60	$914.60