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	$154.67	8.722%	$168.1603	$168.16	$168.15	$168.20
Purchase #2	$134.69	7.822%	$145.2255	$145.23	$145.25	$145.20
Purchase #3	$232.69	13.706%	$264.5825	$264.58	$264.60	$264.60
Purchase #4	$100.58	9.513%	$110.1482	$110.15	$110.15	$110.10
Purchase #5	$167.68	11.597%	$187.1258	$187.13	$187.15	$187.10
Purchase #6	$32.99	8.790%	$35.8898	$35.89	$35.90	$35.90
Purchase #7	$180.61	13.706%	$205.3644	$205.36	$205.35	$205.40
7 purchase totals =	$1,003.91		$1,116.4965	$1,116.50	$1,116.55	$1,116.50