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	$210.51	10.380%	$232.3609	$232.36	$232.35	$232.40
Purchase #2	$218.44	12.604%	$245.9722	$245.97	$245.95	$246.00
Purchase #3	$122.78	13.402%	$139.235	$139.24	$139.25	$139.20
Purchase #4	$37.54	13.735%	$42.6961	$42.70	$42.70	$42.70
Purchase #5	$103.60	7.647%	$111.5223	$111.52	$111.50	$111.50
Purchase #6	$235.79	8.458%	$255.7331	$255.73	$255.75	$255.70
Purchase #7	$154.72	11.194%	$172.0394	$172.04	$172.05	$172.00
7 purchase totals =	$1,083.38		$1,199.5590	$1,199.56	$1,199.55	$1,199.50