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	$237.55	7.477%	$255.3116	$255.31	$255.30	$255.30
Purchase #2	$235.39	3.564%	$243.7793	$243.78	$243.80	$243.80
Purchase #3	$188.54	3.155%	$194.4884	$194.49	$194.50	$194.50
Purchase #4	$114.89	8.733%	$124.9233	$124.92	$124.90	$124.90
Purchase #5	$216.78	13.561%	$246.1775	$246.18	$246.20	$246.20
Purchase #6	$51.67	8.441%	$56.0315	$56.03	$56.05	$56.00
Purchase #7	$9.73	10.514%	$10.753	$10.75	$10.75	$10.80
7 purchase totals =	$1,054.55		$1,131.4646	$1,131.46	$1,131.50	$1,131.50