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	$189.90	3.566%	$196.6718	$196.67	$196.65	$196.70
Purchase #2	$169.70	10.331%	$187.2317	$187.23	$187.25	$187.20
Purchase #3	$115.89	13.445%	$131.4714	$131.47	$131.45	$131.50
Purchase #4	$65.48	11.183%	$72.8026	$72.80	$72.80	$72.80
Purchase #5	$60.27	6.331%	$64.0857	$64.09	$64.10	$64.10
Purchase #6	$32.63	6.213%	$34.6573	$34.66	$34.65	$34.70
Purchase #7	$19.74	9.174%	$21.5509	$21.55	$21.55	$21.60
7 purchase totals =	$653.61		$708.4714	$708.47	$708.45	$708.60