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	$100.34	11.495%	$111.8741	$111.87	$111.85	$111.90
Purchase #2	$174.54	13.498%	$198.0994	$198.10	$198.10	$198.10
Purchase #3	$57.53	11.535%	$64.1661	$64.17	$64.15	$64.20
Purchase #4	$155.64	3.607%	$161.2539	$161.25	$161.25	$161.30
Purchase #5	$141.67	10.477%	$156.5128	$156.51	$156.50	$156.50
Purchase #6	$21.66	10.136%	$23.8555	$23.86	$23.85	$23.90
Purchase #7	$232.56	5.328%	$244.9508	$244.95	$244.95	$245.00
7 purchase totals =	$883.94		$960.7126	$960.71	$960.65	$960.90