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	$129.96	9.673%	$142.531	$142.53	$142.55	$142.50
Purchase #2	$141.66	13.727%	$161.1057	$161.11	$161.10	$161.10
Purchase #3	$101.46	3.565%	$105.077	$105.08	$105.10	$105.10
Purchase #4	$32.39	9.313%	$35.4065	$35.41	$35.40	$35.40
Purchase #5	$50.37	12.202%	$56.5161	$56.52	$56.50	$56.50
Purchase #6	$60.36	3.828%	$62.6706	$62.67	$62.65	$62.70
Purchase #7	$204.51	8.803%	$222.513	$222.51	$222.50	$222.50
7 purchase totals =	$720.71		$785.8199	$785.83	$785.80	$785.80