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	$30.86	4.635%	$32.2904	$32.29	$32.30	$32.30
Purchase #2	$171.89	9.345%	$187.9531	$187.95	$187.95	$188.00
Purchase #3	$195.40	9.185%	$213.3475	$213.35	$213.35	$213.30
Purchase #4	$227.35	13.755%	$258.622	$258.62	$258.60	$258.60
Purchase #5	$246.72	7.274%	$264.6664	$264.67	$264.65	$264.70
Purchase #6	$193.74	13.500%	$219.8949	$219.89	$219.90	$219.90
Purchase #7	$77.47	10.856%	$85.8801	$85.88	$85.90	$85.90
7 purchase totals =	$1,143.43		$1,262.6544	$1,262.65	$1,262.65	$1,262.70