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	$33.77	12.541%	$38.0051	$38.01	$38.00	$38.00
Purchase #2	$143.45	9.660%	$157.3073	$157.31	$157.30	$157.30
Purchase #3	$89.35	3.843%	$92.7837	$92.78	$92.80	$92.80
Purchase #4	$249.28	9.699%	$273.4577	$273.46	$273.45	$273.50
Purchase #5	$191.56	4.480%	$200.1419	$200.14	$200.15	$200.10
Purchase #6	$13.57	11.255%	$15.0973	$15.10	$15.10	$15.10
Purchase #7	$179.82	3.115%	$185.4214	$185.42	$185.40	$185.40
7 purchase totals =	$900.80		$962.2144	$962.22	$962.20	$962.20