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	$239.91	11.673%	$267.9147	$267.91	$267.90	$267.90
Purchase #2	$49.71	7.589%	$53.4825	$53.48	$53.50	$53.50
Purchase #3	$49.37	6.364%	$52.5119	$52.51	$52.50	$52.50
Purchase #4	$202.36	10.145%	$222.8894	$222.89	$222.90	$222.90
Purchase #5	$208.50	7.620%	$224.3877	$224.39	$224.40	$224.40
Purchase #6	$73.58	4.161%	$76.6417	$76.64	$76.65	$76.60
Purchase #7	$118.35	8.783%	$128.7447	$128.74	$128.75	$128.70
7 purchase totals =	$941.78		$1,026.5726	$1,026.56	$1,026.60	$1,026.50