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	$52.88	6.254%	$56.1871	$56.19	$56.20	$56.20
Purchase #2	$40.92	10.366%	$45.1618	$45.16	$45.15	$45.20
Purchase #3	$133.80	12.565%	$150.612	$150.61	$150.60	$150.60
Purchase #4	$119.71	13.650%	$136.0504	$136.05	$136.05	$136.10
Purchase #5	$95.41	3.823%	$99.0575	$99.06	$99.05	$99.10
Purchase #6	$162.51	10.168%	$179.034	$179.03	$179.05	$179.00
Purchase #7	$244.43	12.551%	$275.1084	$275.11	$275.10	$275.10
7 purchase totals =	$849.66		$941.2112	$941.21	$941.20	$941.30