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	$218.48	4.578%	$228.482	$228.48	$228.50	$228.50
Purchase #2	$141.87	13.837%	$161.5006	$161.50	$161.50	$161.50
Purchase #3	$54.45	9.459%	$59.6004	$59.60	$59.60	$59.60
Purchase #4	$231.33	12.525%	$260.3041	$260.30	$260.30	$260.30
Purchase #5	$104.55	9.507%	$114.4896	$114.49	$114.50	$114.50
Purchase #6	$168.80	7.227%	$180.9992	$181.00	$181.00	$181.00
Purchase #7	$30.91	13.858%	$35.1935	$35.19	$35.20	$35.20
7 purchase totals =	$950.39		$1,040.5694	$1,040.56	$1,040.60	$1,040.60