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	$98.71	7.202%	$105.8191	$105.82	$105.80	$105.80
Purchase #2	$144.91	4.619%	$151.6034	$151.60	$151.60	$151.60
Purchase #3	$124.92	10.442%	$137.9641	$137.96	$137.95	$138.00
Purchase #4	$88.72	10.549%	$98.0791	$98.08	$98.10	$98.10
Purchase #5	$131.50	8.433%	$142.5894	$142.59	$142.60	$142.60
Purchase #6	$49.41	3.253%	$51.0173	$51.02	$51.00	$51.00
Purchase #7	$45.77	4.582%	$47.8672	$47.87	$47.85	$47.90
7 purchase totals =	$683.94		$734.9396	$734.94	$734.90	$735.00