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	$190.90	3.670%	$197.906	$197.91	$197.90	$197.90
Purchase #2	$57.50	12.161%	$64.4926	$64.49	$64.50	$64.50
Purchase #3	$130.76	6.698%	$139.5183	$139.52	$139.50	$139.50
Purchase #4	$61.88	4.337%	$64.5637	$64.56	$64.55	$64.60
Purchase #5	$103.58	12.621%	$116.6528	$116.65	$116.65	$116.70
Purchase #6	$29.51	6.575%	$31.4503	$31.45	$31.45	$31.50
Purchase #7	$217.66	11.860%	$243.4745	$243.47	$243.45	$243.50
7 purchase totals =	$791.79		$858.0582	$858.05	$858.00	$858.20