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	$181.40	11.479%	$202.2229	$202.22	$202.20	$202.20
Purchase #2	$53.39	12.188%	$59.8972	$59.90	$59.90	$59.90
Purchase #3	$129.73	7.528%	$139.4961	$139.50	$139.50	$139.50
Purchase #4	$107.68	4.807%	$112.8562	$112.86	$112.85	$112.90
Purchase #5	$132.83	12.662%	$149.6489	$149.65	$149.65	$149.60
Purchase #6	$138.64	7.486%	$149.0186	$149.02	$149.00	$149.00
Purchase #7	$172.77	10.427%	$190.7847	$190.78	$190.80	$190.80
7 purchase totals =	$916.44		$1,003.9246	$1,003.93	$1,003.90	$1,003.90