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	$227.38	6.703%	$242.6213	$242.62	$242.60	$242.60
Purchase #2	$36.66	3.337%	$37.8833	$37.88	$37.90	$37.90
Purchase #3	$203.67	5.286%	$214.436	$214.44	$214.45	$214.40
Purchase #4	$145.50	7.591%	$156.5449	$156.54	$156.55	$156.50
Purchase #5	$210.69	7.106%	$225.6616	$225.66	$225.65	$225.70
Purchase #6	$14.49	7.590%	$15.5898	$15.59	$15.60	$15.60
Purchase #7	$98.61	11.791%	$110.2371	$110.24	$110.25	$110.20
7 purchase totals =	$937.00		$1,002.9740	$1,002.97	$1,003.00	$1,002.90