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	$224.46	8.215%	$242.8994	$242.90	$242.90	$242.90
Purchase #2	$131.43	10.548%	$145.2932	$145.29	$145.30	$145.30
Purchase #3	$47.54	10.154%	$52.3672	$52.37	$52.35	$52.40
Purchase #4	$247.71	6.178%	$263.0135	$263.01	$263.00	$263.00
Purchase #5	$78.86	9.464%	$86.3233	$86.32	$86.30	$86.30
Purchase #6	$206.43	11.139%	$229.4242	$229.42	$229.40	$229.40
Purchase #7	$125.93	4.453%	$131.5377	$131.54	$131.55	$131.50
7 purchase totals =	$1,062.36		$1,150.8585	$1,150.85	$1,150.80	$1,150.80