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	$236.82	4.240%	$246.8612	$246.86	$246.85	$246.90
Purchase #2	$114.46	12.270%	$128.5042	$128.50	$128.50	$128.50
Purchase #3	$35.80	13.812%	$40.7447	$40.74	$40.75	$40.70
Purchase #4	$211.72	12.663%	$238.5301	$238.53	$238.55	$238.50
Purchase #5	$83.72	13.132%	$94.7141	$94.71	$94.70	$94.70
Purchase #6	$201.81	8.467%	$218.8973	$218.90	$218.90	$218.90
Purchase #7	$167.49	9.602%	$183.5724	$183.57	$183.55	$183.60
7 purchase totals =	$1,051.82		$1,151.8240	$1,151.81	$1,151.80	$1,151.80