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	$140.59	4.288%	$146.6185	$146.62	$146.60	$146.60
Purchase #2	$70.57	11.780%	$78.8831	$78.88	$78.90	$78.90
Purchase #3	$160.61	6.474%	$171.0079	$171.01	$171.00	$171.00
Purchase #4	$23.59	12.398%	$26.5147	$26.51	$26.50	$26.50
Purchase #5	$78.43	8.705%	$85.2573	$85.26	$85.25	$85.30
Purchase #6	$64.40	3.198%	$66.4595	$66.46	$66.45	$66.50
Purchase #7	$36.56	9.247%	$39.9407	$39.94	$39.95	$39.90
7 purchase totals =	$574.75		$614.6817	$614.68	$614.65	$614.70