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	$169.26	3.103%	$174.5121	$174.51	$174.50	$174.50
Purchase #2	$102.38	12.109%	$114.7772	$114.78	$114.80	$114.80
Purchase #3	$198.75	8.564%	$215.771	$215.77	$215.75	$215.80
Purchase #4	$231.72	6.224%	$246.1423	$246.14	$246.15	$246.10
Purchase #5	$86.29	3.824%	$89.5897	$89.59	$89.60	$89.60
Purchase #6	$31.96	10.147%	$35.203	$35.20	$35.20	$35.20
Purchase #7	$135.56	4.435%	$141.5721	$141.57	$141.55	$141.60
7 purchase totals =	$955.92		$1,017.5674	$1,017.56	$1,017.55	$1,017.60