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	$237.48	7.448%	$255.1675	$255.17	$255.15	$255.20
Purchase #2	$217.86	7.560%	$234.3302	$234.33	$234.35	$234.30
Purchase #3	$107.48	6.824%	$114.8144	$114.81	$114.80	$114.80
Purchase #4	$240.89	12.604%	$271.2518	$271.25	$271.25	$271.30
Purchase #5	$195.83	11.718%	$218.7774	$218.78	$218.80	$218.80
Purchase #6	$114.49	4.768%	$119.9489	$119.95	$119.95	$119.90
Purchase #7	$46.79	8.115%	$50.587	$50.59	$50.60	$50.60
7 purchase totals =	$1,160.82		$1,264.8772	$1,264.88	$1,264.90	$1,264.90