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	$167.81	7.517%	$180.4243	$180.42	$180.40	$180.40
Purchase #2	$166.91	13.386%	$189.2526	$189.25	$189.25	$189.30
Purchase #3	$232.65	4.279%	$242.6051	$242.61	$242.60	$242.60
Purchase #4	$59.53	9.404%	$65.1282	$65.13	$65.15	$65.10
Purchase #5	$113.43	10.358%	$125.1791	$125.18	$125.20	$125.20
Purchase #6	$189.33	3.745%	$196.4204	$196.42	$196.40	$196.40
Purchase #7	$87.62	8.294%	$94.8872	$94.89	$94.90	$94.90
7 purchase totals =	$1,017.28		$1,093.8969	$1,093.90	$1,093.90	$1,093.90