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	$211.34	7.871%	$227.9746	$227.97	$227.95	$228.00
Purchase #2	$245.78	7.357%	$263.862	$263.86	$263.85	$263.90
Purchase #3	$41.32	13.434%	$46.8709	$46.87	$46.85	$46.90
Purchase #4	$203.54	9.456%	$222.7867	$222.79	$222.80	$222.80
Purchase #5	$114.52	3.319%	$118.3209	$118.32	$118.30	$118.30
Purchase #6	$211.40	10.635%	$233.8824	$233.88	$233.90	$233.90
Purchase #7	$100.50	8.689%	$109.2324	$109.23	$109.25	$109.20
7 purchase totals =	$1,128.40		$1,222.9299	$1,222.92	$1,222.90	$1,223.00