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	$122.61	7.208%	$131.4477	$131.45	$131.45	$131.40
Purchase #2	$181.27	6.728%	$193.4658	$193.47	$193.45	$193.50
Purchase #3	$238.66	11.797%	$266.8147	$266.81	$266.80	$266.80
Purchase #4	$162.96	13.616%	$185.1486	$185.15	$185.15	$185.10
Purchase #5	$197.39	11.724%	$220.532	$220.53	$220.55	$220.50
Purchase #6	$88.91	6.299%	$94.5104	$94.51	$94.50	$94.50
Purchase #7	$93.73	6.738%	$100.0455	$100.05	$100.05	$100.00
7 purchase totals =	$1,085.53		$1,191.9647	$1,191.97	$1,191.95	$1,191.80