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	$126.32	3.709%	$131.0052	$131.01	$131.00	$131.00
Purchase #2	$166.50	5.366%	$175.4344	$175.43	$175.45	$175.40
Purchase #3	$147.79	6.665%	$157.6402	$157.64	$157.65	$157.60
Purchase #4	$133.28	8.626%	$144.7767	$144.78	$144.80	$144.80
Purchase #5	$150.65	6.821%	$160.9258	$160.93	$160.95	$160.90
Purchase #6	$30.72	8.399%	$33.3002	$33.30	$33.30	$33.30
Purchase #7	$53.94	9.773%	$59.2116	$59.21	$59.20	$59.20
7 purchase totals =	$809.20		$862.2941	$862.30	$862.35	$862.20