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	$87.40	13.384%	$99.0976	$99.10	$99.10	$99.10
Purchase #2	$215.86	3.355%	$223.1021	$223.10	$223.10	$223.10
Purchase #3	$11.61	13.235%	$13.1466	$13.15	$13.15	$13.10
Purchase #4	$180.26	11.396%	$200.8024	$200.80	$200.80	$200.80
Purchase #5	$211.44	6.855%	$225.9342	$225.93	$225.95	$225.90
Purchase #6	$242.80	5.305%	$255.6805	$255.68	$255.70	$255.70
Purchase #7	$129.77	3.219%	$133.9473	$133.95	$133.95	$133.90
7 purchase totals =	$1,079.14		$1,151.7107	$1,151.71	$1,151.75	$1,151.60