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	$227.35	9.474%	$248.8891	$248.89	$248.90	$248.90
Purchase #2	$211.61	13.653%	$240.5011	$240.50	$240.50	$240.50
Purchase #3	$18.42	5.791%	$19.4867	$19.49	$19.50	$19.50
Purchase #4	$40.46	4.743%	$42.379	$42.38	$42.40	$42.40
Purchase #5	$132.96	9.432%	$145.5008	$145.50	$145.50	$145.50
Purchase #6	$55.74	3.139%	$57.4897	$57.49	$57.50	$57.50
Purchase #7	$187.35	11.500%	$208.8953	$208.90	$208.90	$208.90
7 purchase totals =	$873.89		$963.1417	$963.15	$963.20	$963.20