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	$205.51	8.281%	$222.5283	$222.53	$222.55	$222.50
Purchase #2	$69.92	10.197%	$77.0497	$77.05	$77.05	$77.00
Purchase #3	$85.46	11.827%	$95.5674	$95.57	$95.55	$95.60
Purchase #4	$109.79	13.863%	$125.0102	$125.01	$125.00	$125.00
Purchase #5	$190.72	12.375%	$214.3216	$214.32	$214.30	$214.30
Purchase #6	$190.60	11.170%	$211.89	$211.89	$211.90	$211.90
Purchase #7	$238.83	6.843%	$255.1731	$255.17	$255.15	$255.20
7 purchase totals =	$1,090.83		$1,201.5403	$1,201.54	$1,201.50	$1,201.50