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	$208.73	11.128%	$231.9575	$231.96	$231.95	$232.00
Purchase #2	$143.83	5.490%	$151.7263	$151.73	$151.75	$151.70
Purchase #3	$64.44	12.234%	$72.3236	$72.32	$72.30	$72.30
Purchase #4	$63.36	3.478%	$65.5637	$65.56	$65.55	$65.60
Purchase #5	$134.71	12.198%	$151.1419	$151.14	$151.15	$151.10
Purchase #6	$114.44	4.563%	$119.6619	$119.66	$119.65	$119.70
Purchase #7	$42.32	4.176%	$44.0873	$44.09	$44.10	$44.10
7 purchase totals =	$771.83		$836.4622	$836.46	$836.45	$836.50