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	$61.96	11.784%	$69.2614	$69.26	$69.25	$69.30
Purchase #2	$94.48	3.537%	$97.8218	$97.82	$97.80	$97.80
Purchase #3	$29.83	13.736%	$33.9274	$33.93	$33.95	$33.90
Purchase #4	$91.48	12.431%	$102.8519	$102.85	$102.85	$102.90
Purchase #5	$67.35	5.665%	$71.1654	$71.17	$71.15	$71.20
Purchase #6	$156.32	12.537%	$175.9178	$175.92	$175.90	$175.90
Purchase #7	$160.47	7.666%	$172.7716	$172.77	$172.75	$172.80
7 purchase totals =	$661.89		$723.7173	$723.72	$723.65	$723.80