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	$207.62	5.479%	$218.9955	$219.00	$219.00	$219.00
Purchase #2	$171.34	11.765%	$191.4982	$191.50	$191.50	$191.50
Purchase #3	$94.87	7.650%	$102.1276	$102.13	$102.15	$102.10
Purchase #4	$18.98	4.230%	$19.7829	$19.78	$19.80	$19.80
Purchase #5	$29.83	7.305%	$32.0091	$32.01	$32.00	$32.00
Purchase #6	$161.55	6.757%	$172.4659	$172.47	$172.45	$172.50
Purchase #7	$82.57	8.563%	$89.6405	$89.64	$89.65	$89.60
7 purchase totals =	$766.76		$826.5197	$826.53	$826.55	$826.50