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	$30.82	6.232%	$32.7407	$32.74	$32.75	$32.70
Purchase #2	$78.55	4.739%	$82.2725	$82.27	$82.25	$82.30
Purchase #3	$105.75	3.822%	$109.7918	$109.79	$109.80	$109.80
Purchase #4	$122.54	3.844%	$127.2504	$127.25	$127.25	$127.30
Purchase #5	$6.86	3.847%	$7.1239	$7.12	$7.10	$7.10
Purchase #6	$95.48	6.149%	$101.3511	$101.35	$101.35	$101.40
Purchase #7	$247.97	3.386%	$256.3663	$256.37	$256.35	$256.40
7 purchase totals =	$687.97		$716.8967	$716.89	$716.85	$717.00