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	$223.90	7.110%	$239.8193	$239.82	$239.80	$239.80
Purchase #2	$14.80	4.621%	$15.4839	$15.48	$15.50	$15.50
Purchase #3	$29.31	8.261%	$31.7313	$31.73	$31.75	$31.70
Purchase #4	$219.82	6.417%	$233.9258	$233.93	$233.95	$233.90
Purchase #5	$70.46	6.634%	$75.1343	$75.13	$75.15	$75.10
Purchase #6	$109.48	13.137%	$123.8624	$123.86	$123.85	$123.90
Purchase #7	$35.75	12.327%	$40.1569	$40.16	$40.15	$40.20
7 purchase totals =	$703.52		$760.1139	$760.11	$760.15	$760.10