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	$86.99	9.844%	$95.5533	$95.55	$95.55	$95.60
Purchase #2	$59.96	12.184%	$67.2655	$67.27	$67.25	$67.30
Purchase #3	$169.38	6.278%	$180.0137	$180.01	$180.00	$180.00
Purchase #4	$67.27	7.489%	$72.3079	$72.31	$72.30	$72.30
Purchase #5	$159.96	9.452%	$175.0794	$175.08	$175.10	$175.10
Purchase #6	$87.50	3.323%	$90.4076	$90.41	$90.40	$90.40
Purchase #7	$137.54	7.318%	$147.6052	$147.61	$147.60	$147.60
7 purchase totals =	$768.60		$828.2326	$828.24	$828.20	$828.30