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	$229.60	6.276%	$244.0097	$244.01	$244.00	$244.00
Purchase #2	$132.47	6.443%	$141.005	$141.01	$141.00	$141.00
Purchase #3	$95.64	8.486%	$103.756	$103.76	$103.75	$103.80
Purchase #4	$114.76	8.576%	$124.6018	$124.60	$124.60	$124.60
Purchase #5	$148.66	12.710%	$167.5547	$167.55	$167.55	$167.60
Purchase #6	$114.76	7.214%	$123.0388	$123.04	$123.05	$123.00
Purchase #7	$87.40	13.382%	$99.0959	$99.10	$99.10	$99.10
7 purchase totals =	$923.29		$1,003.0619	$1,003.07	$1,003.05	$1,003.10