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	$22.97	9.297%	$25.1055	$25.11	$25.10	$25.10
Purchase #2	$206.27	13.299%	$233.7018	$233.70	$233.70	$233.70
Purchase #3	$114.81	7.678%	$123.6251	$123.63	$123.65	$123.60
Purchase #4	$167.46	7.767%	$180.4666	$180.47	$180.45	$180.50
Purchase #5	$90.67	10.665%	$100.34	$100.34	$100.35	$100.30
Purchase #6	$139.50	5.503%	$147.1767	$147.18	$147.20	$147.20
Purchase #7	$95.96	10.234%	$105.7805	$105.78	$105.80	$105.80
7 purchase totals =	$837.64		$916.1962	$916.21	$916.25	$916.20