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	$96.50	8.622%	$104.8202	$104.82	$104.80	$104.80
Purchase #2	$6.90	5.666%	$7.291	$7.29	$7.30	$7.30
Purchase #3	$233.36	13.660%	$265.237	$265.24	$265.25	$265.20
Purchase #4	$205.92	4.249%	$214.6695	$214.67	$214.65	$214.70
Purchase #5	$30.34	8.161%	$32.816	$32.82	$32.80	$32.80
Purchase #6	$80.72	5.712%	$85.3307	$85.33	$85.35	$85.30
Purchase #7	$88.44	3.695%	$91.7079	$91.71	$91.70	$91.70
7 purchase totals =	$742.18		$801.8723	$801.88	$801.85	$801.80