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	$207.42	3.549%	$214.7813	$214.78	$214.80	$214.80
Purchase #2	$63.88	12.173%	$71.6561	$71.66	$71.65	$71.70
Purchase #3	$38.89	8.547%	$42.2139	$42.21	$42.20	$42.20
Purchase #4	$101.87	6.287%	$108.2746	$108.27	$108.25	$108.30
Purchase #5	$76.29	8.438%	$82.7274	$82.73	$82.75	$82.70
Purchase #6	$62.72	7.644%	$67.5143	$67.51	$67.50	$67.50
Purchase #7	$213.93	7.462%	$229.8935	$229.89	$229.90	$229.90
7 purchase totals =	$765.00		$817.0611	$817.05	$817.05	$817.10