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	$90.43	8.706%	$98.3028	$98.30	$98.30	$98.30
Purchase #2	$161.85	13.815%	$184.2096	$184.21	$184.20	$184.20
Purchase #3	$128.89	7.129%	$138.0786	$138.08	$138.10	$138.10
Purchase #4	$213.80	11.437%	$238.2523	$238.25	$238.25	$238.30
Purchase #5	$63.83	3.103%	$65.8106	$65.81	$65.80	$65.80
Purchase #6	$131.76	4.708%	$137.9633	$137.96	$137.95	$138.00
Purchase #7	$190.67	4.275%	$198.8211	$198.82	$198.80	$198.80
7 purchase totals =	$981.23		$1,061.4383	$1,061.43	$1,061.40	$1,061.50