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	$160.55	11.793%	$179.4837	$179.48	$179.50	$179.50
Purchase #2	$141.67	6.604%	$151.0259	$151.03	$151.05	$151.00
Purchase #3	$26.53	7.194%	$28.4386	$28.44	$28.45	$28.40
Purchase #4	$122.61	7.311%	$131.574	$131.57	$131.55	$131.60
Purchase #5	$93.53	10.702%	$103.5396	$103.54	$103.55	$103.50
Purchase #6	$133.37	8.283%	$144.417	$144.42	$144.40	$144.40
Purchase #7	$150.68	11.718%	$168.3367	$168.34	$168.35	$168.30
7 purchase totals =	$828.94		$906.8155	$906.82	$906.85	$906.70