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	$38.34	12.392%	$43.0911	$43.09	$43.10	$43.10
Purchase #2	$35.79	6.304%	$38.0462	$38.05	$38.05	$38.00
Purchase #3	$52.82	7.496%	$56.7794	$56.78	$56.80	$56.80
Purchase #4	$28.27	10.223%	$31.16	$31.16	$31.15	$31.20
Purchase #5	$172.54	11.429%	$192.2596	$192.26	$192.25	$192.30
Purchase #6	$250.44	10.780%	$277.4374	$277.44	$277.45	$277.40
Purchase #7	$102.80	11.413%	$114.5326	$114.53	$114.55	$114.50
7 purchase totals =	$681.00		$753.3063	$753.31	$753.35	$753.30