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	$84.87	4.103%	$88.3522	$88.35	$88.35	$88.40
Purchase #2	$110.72	8.271%	$119.8777	$119.88	$119.90	$119.90
Purchase #3	$49.31	12.710%	$55.5773	$55.58	$55.60	$55.60
Purchase #4	$85.29	5.674%	$90.1294	$90.13	$90.15	$90.10
Purchase #5	$82.91	13.618%	$94.2007	$94.20	$94.20	$94.20
Purchase #6	$160.99	3.409%	$166.4781	$166.48	$166.50	$166.50
Purchase #7	$101.42	4.459%	$105.9423	$105.94	$105.95	$105.90
7 purchase totals =	$675.51		$720.5577	$720.56	$720.65	$720.60