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	$85.44	9.403%	$93.4739	$93.47	$93.45	$93.50
Purchase #2	$82.55	12.292%	$92.697	$92.70	$92.70	$92.70
Purchase #3	$200.85	10.352%	$221.642	$221.64	$221.65	$221.60
Purchase #4	$146.90	6.458%	$156.3868	$156.39	$156.40	$156.40
Purchase #5	$128.46	10.591%	$142.0652	$142.07	$142.05	$142.10
Purchase #6	$41.45	10.540%	$45.8188	$45.82	$45.80	$45.80
Purchase #7	$99.49	9.756%	$109.1962	$109.20	$109.20	$109.20
7 purchase totals =	$785.14		$861.2799	$861.29	$861.25	$861.30