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	$174.51	9.379%	$190.8773	$190.88	$190.90	$190.90
Purchase #2	$44.91	6.651%	$47.897	$47.90	$47.90	$47.90
Purchase #3	$115.99	13.764%	$131.9549	$131.95	$131.95	$132.00
Purchase #4	$237.48	8.629%	$257.9721	$257.97	$257.95	$258.00
Purchase #5	$168.40	13.119%	$190.4924	$190.49	$190.50	$190.50
Purchase #6	$37.49	12.468%	$42.1643	$42.16	$42.15	$42.20
Purchase #7	$179.72	4.423%	$187.669	$187.67	$187.65	$187.70
7 purchase totals =	$958.50		$1,049.0270	$1,049.02	$1,049.00	$1,049.20