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	$98.82	13.344%	$112.0065	$112.01	$112.00	$112.00
Purchase #2	$30.75	12.286%	$34.5279	$34.53	$34.55	$34.50
Purchase #3	$23.87	4.554%	$24.957	$24.96	$24.95	$25.00
Purchase #4	$76.78	12.798%	$86.6063	$86.61	$86.60	$86.60
Purchase #5	$53.41	11.105%	$59.3412	$59.34	$59.35	$59.30
Purchase #6	$103.42	7.586%	$111.2654	$111.27	$111.25	$111.30
Purchase #7	$67.94	8.160%	$73.4839	$73.48	$73.50	$73.50
7 purchase totals =	$454.99		$502.1882	$502.20	$502.20	$502.20