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	$75.33	9.662%	$82.6084	$82.61	$82.60	$82.60
Purchase #2	$114.35	11.396%	$127.3813	$127.38	$127.40	$127.40
Purchase #3	$232.50	6.190%	$246.8918	$246.89	$246.90	$246.90
Purchase #4	$9.67	5.134%	$10.1665	$10.17	$10.15	$10.20
Purchase #5	$203.41	8.749%	$221.2063	$221.21	$221.20	$221.20
Purchase #6	$246.98	8.422%	$267.7807	$267.78	$267.80	$267.80
Purchase #7	$109.48	13.207%	$123.939	$123.94	$123.95	$123.90
7 purchase totals =	$991.72		$1,079.9740	$1,079.98	$1,080.00	$1,080.00