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	$226.92	12.576%	$255.4575	$255.46	$255.45	$255.50
Purchase #2	$9.70	12.488%	$10.9113	$10.91	$10.90	$10.90
Purchase #3	$14.30	6.109%	$15.1736	$15.17	$15.15	$15.20
Purchase #4	$85.55	7.674%	$92.1151	$92.12	$92.10	$92.10
Purchase #5	$40.33	3.384%	$41.6948	$41.69	$41.70	$41.70
Purchase #6	$141.41	12.761%	$159.4553	$159.46	$159.45	$159.50
Purchase #7	$54.93	5.850%	$58.1434	$58.14	$58.15	$58.10
7 purchase totals =	$573.14		$632.9510	$632.95	$632.90	$633.00