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	$83.46	7.186%	$89.4574	$89.46	$89.45	$89.50
Purchase #2	$213.98	6.514%	$227.9187	$227.92	$227.90	$227.90
Purchase #3	$83.59	3.460%	$86.4822	$86.48	$86.50	$86.50
Purchase #4	$100.78	13.224%	$114.1071	$114.11	$114.10	$114.10
Purchase #5	$225.51	4.457%	$235.561	$235.56	$235.55	$235.60
Purchase #6	$204.38	6.257%	$217.1681	$217.17	$217.15	$217.20
Purchase #7	$191.40	8.601%	$207.8623	$207.86	$207.85	$207.90
7 purchase totals =	$1,103.10		$1,178.5568	$1,178.56	$1,178.50	$1,178.70