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	$144.86	10.404%	$159.9312	$159.93	$159.95	$159.90
Purchase #2	$67.61	11.483%	$75.3737	$75.37	$75.35	$75.40
Purchase #3	$201.86	7.133%	$216.2587	$216.26	$216.25	$216.30
Purchase #4	$98.86	13.188%	$111.8977	$111.90	$111.90	$111.90
Purchase #5	$173.70	9.845%	$190.8008	$190.80	$190.80	$190.80
Purchase #6	$145.27	5.237%	$152.8778	$152.88	$152.90	$152.90
Purchase #7	$200.56	7.602%	$215.8066	$215.81	$215.80	$215.80
7 purchase totals =	$1,032.72		$1,122.9465	$1,122.95	$1,122.95	$1,123.00