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	$245.76	7.615%	$264.4746	$264.47	$264.45	$264.50
Purchase #2	$37.58	7.618%	$40.4428	$40.44	$40.45	$40.40
Purchase #3	$192.33	10.139%	$211.8303	$211.83	$211.85	$211.80
Purchase #4	$18.27	13.340%	$20.7072	$20.71	$20.70	$20.70
Purchase #5	$145.56	3.284%	$150.3402	$150.34	$150.35	$150.30
Purchase #6	$157.25	7.391%	$168.8723	$168.87	$168.85	$168.90
Purchase #7	$84.87	5.323%	$89.3876	$89.39	$89.40	$89.40
7 purchase totals =	$881.62		$946.0550	$946.05	$946.05	$946.00