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	$43.63	8.460%	$47.3211	$47.32	$47.30	$47.30
Purchase #2	$185.55	13.581%	$210.7495	$210.75	$210.75	$210.70
Purchase #3	$44.46	3.372%	$45.9592	$45.96	$45.95	$46.00
Purchase #4	$31.49	6.497%	$33.5359	$33.54	$33.55	$33.50
Purchase #5	$189.98	13.179%	$215.0175	$215.02	$215.00	$215.00
Purchase #6	$11.60	8.548%	$12.5916	$12.59	$12.60	$12.60
Purchase #7	$233.83	11.338%	$260.3416	$260.34	$260.35	$260.30
7 purchase totals =	$740.54		$825.5164	$825.52	$825.50	$825.40