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	$237.81	4.214%	$247.8313	$247.83	$247.85	$247.80
Purchase #2	$61.61	10.165%	$67.8727	$67.87	$67.85	$67.90
Purchase #3	$195.85	11.763%	$218.8878	$218.89	$218.90	$218.90
Purchase #4	$185.32	11.249%	$206.1666	$206.17	$206.15	$206.20
Purchase #5	$109.56	9.177%	$119.6143	$119.61	$119.60	$119.60
Purchase #6	$94.50	6.380%	$100.5291	$100.53	$100.55	$100.50
Purchase #7	$168.87	10.386%	$186.4088	$186.41	$186.40	$186.40
7 purchase totals =	$1,053.52		$1,147.3106	$1,147.31	$1,147.30	$1,147.30