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	$110.35	13.418%	$125.1568	$125.16	$125.15	$125.20
Purchase #2	$167.36	13.783%	$190.4272	$190.43	$190.45	$190.40
Purchase #3	$19.53	4.317%	$20.3731	$20.37	$20.35	$20.40
Purchase #4	$216.58	11.574%	$241.647	$241.65	$241.65	$241.60
Purchase #5	$233.45	6.263%	$248.071	$248.07	$248.05	$248.10
Purchase #6	$17.30	9.206%	$18.8926	$18.89	$18.90	$18.90
Purchase #7	$166.78	12.185%	$187.1021	$187.10	$187.10	$187.10
7 purchase totals =	$931.35		$1,031.6698	$1,031.67	$1,031.65	$1,031.70