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	$180.77	11.181%	$200.9819	$200.98	$201.00	$201.00
Purchase #2	$48.43	10.661%	$53.5931	$53.59	$53.60	$53.60
Purchase #3	$147.70	3.134%	$152.3289	$152.33	$152.35	$152.30
Purchase #4	$209.29	10.588%	$231.4496	$231.45	$231.45	$231.40
Purchase #5	$19.74	4.186%	$20.5663	$20.57	$20.55	$20.60
Purchase #6	$75.85	8.459%	$82.2662	$82.27	$82.25	$82.30
Purchase #7	$122.93	5.168%	$129.283	$129.28	$129.30	$129.30
7 purchase totals =	$804.71		$870.4690	$870.47	$870.50	$870.50