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	$198.78	10.531%	$219.7135	$219.71	$219.70	$219.70
Purchase #2	$51.56	5.305%	$54.2953	$54.30	$54.30	$54.30
Purchase #3	$12.54	10.561%	$13.8643	$13.86	$13.85	$13.90
Purchase #4	$202.80	6.654%	$216.2943	$216.29	$216.30	$216.30
Purchase #5	$222.58	5.519%	$234.8642	$234.86	$234.85	$234.90
Purchase #6	$33.53	6.729%	$35.7862	$35.79	$35.80	$35.80
Purchase #7	$49.64	13.731%	$56.4561	$56.46	$56.45	$56.50
7 purchase totals =	$771.43		$831.2739	$831.27	$831.25	$831.40