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	$38.89	13.195%	$44.0215	$44.02	$44.00	$44.00
Purchase #2	$17.82	9.537%	$19.5195	$19.52	$19.50	$19.50
Purchase #3	$99.28	4.216%	$103.4656	$103.47	$103.45	$103.50
Purchase #4	$216.51	8.300%	$234.4803	$234.48	$234.50	$234.50
Purchase #5	$66.72	10.327%	$73.6102	$73.61	$73.60	$73.60
Purchase #6	$18.63	4.421%	$19.4536	$19.45	$19.45	$19.50
Purchase #7	$223.33	12.361%	$250.9358	$250.94	$250.95	$250.90
7 purchase totals =	$681.18		$745.4865	$745.49	$745.45	$745.50