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	$164.75	4.521%	$172.1983	$172.20	$172.20	$172.20
Purchase #2	$77.76	12.401%	$87.403	$87.40	$87.40	$87.40
Purchase #3	$201.90	13.569%	$229.2958	$229.30	$229.30	$229.30
Purchase #4	$20.54	5.148%	$21.5974	$21.60	$21.60	$21.60
Purchase #5	$104.72	8.108%	$113.2107	$113.21	$113.20	$113.20
Purchase #6	$245.87	6.490%	$261.827	$261.83	$261.85	$261.80
Purchase #7	$159.58	13.644%	$181.3531	$181.35	$181.35	$181.40
7 purchase totals =	$975.12		$1,066.8853	$1,066.89	$1,066.90	$1,066.90