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	$172.45	11.145%	$191.6696	$191.67	$191.65	$191.70
Purchase #2	$229.26	13.171%	$259.4558	$259.46	$259.45	$259.50
Purchase #3	$52.32	13.581%	$59.4256	$59.43	$59.45	$59.40
Purchase #4	$24.57	5.366%	$25.8884	$25.89	$25.90	$25.90
Purchase #5	$219.70	7.254%	$235.637	$235.64	$235.65	$235.60
Purchase #6	$35.76	7.677%	$38.5053	$38.51	$38.50	$38.50
Purchase #7	$166.33	7.870%	$179.4202	$179.42	$179.40	$179.40
7 purchase totals =	$900.39		$990.0019	$990.02	$990.00	$990.00