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	$233.33	7.496%	$250.8204	$250.82	$250.80	$250.80
Purchase #2	$185.45	4.557%	$193.901	$193.90	$193.90	$193.90
Purchase #3	$82.85	3.561%	$85.8003	$85.80	$85.80	$85.80
Purchase #4	$140.72	7.783%	$151.6722	$151.67	$151.65	$151.70
Purchase #5	$90.83	9.631%	$99.5778	$99.58	$99.60	$99.60
Purchase #6	$34.51	3.874%	$35.8469	$35.85	$35.85	$35.80
Purchase #7	$206.50	7.861%	$222.733	$222.73	$222.75	$222.70
7 purchase totals =	$974.19		$1,040.3516	$1,040.35	$1,040.35	$1,040.30