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	$104.57	10.388%	$115.4327	$115.43	$115.45	$115.40
Purchase #2	$147.52	6.228%	$156.7075	$156.71	$156.70	$156.70
Purchase #3	$37.71	13.327%	$42.7356	$42.74	$42.75	$42.70
Purchase #4	$95.94	8.286%	$103.8896	$103.89	$103.90	$103.90
Purchase #5	$32.71	5.175%	$34.4027	$34.40	$34.40	$34.40
Purchase #6	$219.44	4.753%	$229.87	$229.87	$229.85	$229.90
Purchase #7	$61.67	7.652%	$66.389	$66.39	$66.40	$66.40
7 purchase totals =	$699.56		$749.4271	$749.43	$749.45	$749.40