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	$103.35	10.126%	$113.8152	$113.82	$113.80	$113.80
Purchase #2	$136.98	6.483%	$145.8604	$145.86	$145.85	$145.90
Purchase #3	$71.67	13.180%	$81.1161	$81.12	$81.10	$81.10
Purchase #4	$185.72	12.238%	$208.4484	$208.45	$208.45	$208.40
Purchase #5	$229.57	9.161%	$250.6009	$250.60	$250.60	$250.60
Purchase #6	$78.47	5.760%	$82.9899	$82.99	$83.00	$83.00
Purchase #7	$243.80	7.830%	$262.8895	$262.89	$262.90	$262.90
7 purchase totals =	$1,049.56		$1,145.7204	$1,145.73	$1,145.70	$1,145.70