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	$58.97	7.376%	$63.3196	$63.32	$63.30	$63.30
Purchase #2	$190.39	12.261%	$213.7337	$213.73	$213.75	$213.70
Purchase #3	$58.41	13.801%	$66.4712	$66.47	$66.45	$66.50
Purchase #4	$39.88	13.626%	$45.314	$45.31	$45.30	$45.30
Purchase #5	$84.80	7.463%	$91.1286	$91.13	$91.15	$91.10
Purchase #6	$122.45	13.525%	$139.0114	$139.01	$139.00	$139.00
Purchase #7	$109.39	3.203%	$112.8938	$112.89	$112.90	$112.90
7 purchase totals =	$664.29		$731.8723	$731.86	$731.85	$731.80