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	$218.91	11.588%	$244.2773	$244.28	$244.30	$244.30
Purchase #2	$6.90	11.811%	$7.715	$7.72	$7.70	$7.70
Purchase #3	$176.89	5.652%	$186.8878	$186.89	$186.90	$186.90
Purchase #4	$206.51	4.109%	$214.9955	$215.00	$215.00	$215.00
Purchase #5	$187.81	5.506%	$198.1508	$198.15	$198.15	$198.20
Purchase #6	$180.85	10.762%	$200.3131	$200.31	$200.30	$200.30
Purchase #7	$35.95	5.432%	$37.9028	$37.90	$37.90	$37.90
7 purchase totals =	$1,013.82		$1,090.2423	$1,090.25	$1,090.25	$1,090.30