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	$193.89	13.216%	$219.5145	$219.51	$219.50	$219.50
Purchase #2	$165.37	4.543%	$172.8828	$172.88	$172.90	$172.90
Purchase #3	$92.60	3.255%	$95.6141	$95.61	$95.60	$95.60
Purchase #4	$236.87	3.866%	$246.0274	$246.03	$246.05	$246.00
Purchase #5	$37.73	5.756%	$39.9017	$39.90	$39.90	$39.90
Purchase #6	$105.39	13.507%	$119.625	$119.63	$119.65	$119.60
Purchase #7	$234.41	7.255%	$251.4164	$251.42	$251.40	$251.40
7 purchase totals =	$1,066.26		$1,144.9819	$1,144.98	$1,145.00	$1,144.90