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	$228.65	9.534%	$250.4495	$250.45	$250.45	$250.40
Purchase #2	$130.89	8.143%	$141.5484	$141.55	$141.55	$141.50
Purchase #3	$121.85	4.246%	$127.0238	$127.02	$127.00	$127.00
Purchase #4	$229.57	3.678%	$238.0136	$238.01	$238.00	$238.00
Purchase #5	$134.81	11.505%	$150.3199	$150.32	$150.30	$150.30
Purchase #6	$127.51	10.591%	$141.0146	$141.01	$141.00	$141.00
Purchase #7	$82.63	13.544%	$93.8214	$93.82	$93.80	$93.80
7 purchase totals =	$1,055.91		$1,142.1912	$1,142.18	$1,142.10	$1,142.00