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	$40.42	5.620%	$42.6916	$42.69	$42.70	$42.70
Purchase #2	$183.83	7.175%	$197.0198	$197.02	$197.00	$197.00
Purchase #3	$37.44	6.496%	$39.8721	$39.87	$39.85	$39.90
Purchase #4	$217.59	5.115%	$228.7197	$228.72	$228.70	$228.70
Purchase #5	$233.90	12.843%	$263.9398	$263.94	$263.95	$263.90
Purchase #6	$40.25	5.303%	$42.3845	$42.38	$42.40	$42.40
Purchase #7	$215.60	5.517%	$227.4947	$227.49	$227.50	$227.50
7 purchase totals =	$969.03		$1,042.1222	$1,042.11	$1,042.10	$1,042.10