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	$114.58	10.474%	$126.5811	$126.58	$126.60	$126.60
Purchase #2	$35.73	11.273%	$39.7578	$39.76	$39.75	$39.80
Purchase #3	$126.61	5.690%	$133.8141	$133.81	$133.80	$133.80
Purchase #4	$132.37	7.372%	$142.1283	$142.13	$142.15	$142.10
Purchase #5	$132.37	7.564%	$142.3825	$142.38	$142.40	$142.40
Purchase #6	$64.49	10.306%	$71.1363	$71.14	$71.15	$71.10
Purchase #7	$176.35	13.653%	$200.4271	$200.43	$200.45	$200.40
7 purchase totals =	$782.50		$856.2272	$856.23	$856.30	$856.20