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	$78.56	3.414%	$81.242	$81.24	$81.25	$81.20
Purchase #2	$133.81	7.625%	$144.013	$144.01	$144.00	$144.00
Purchase #3	$32.34	10.602%	$35.7687	$35.77	$35.75	$35.80
Purchase #4	$22.42	6.368%	$23.8477	$23.85	$23.85	$23.80
Purchase #5	$73.65	11.550%	$82.1566	$82.16	$82.15	$82.20
Purchase #6	$11.92	5.398%	$12.5634	$12.56	$12.55	$12.60
Purchase #7	$80.83	5.526%	$85.2967	$85.30	$85.30	$85.30
7 purchase totals =	$433.53		$464.8881	$464.89	$464.85	$464.90