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	$77.74	6.203%	$82.5622	$82.56	$82.55	$82.60
Purchase #2	$239.51	6.677%	$255.5021	$255.50	$255.50	$255.50
Purchase #3	$72.34	11.498%	$80.6577	$80.66	$80.65	$80.70
Purchase #4	$142.83	13.204%	$161.6893	$161.69	$161.70	$161.70
Purchase #5	$179.54	11.191%	$199.6323	$199.63	$199.65	$199.60
Purchase #6	$85.36	4.509%	$89.2089	$89.21	$89.20	$89.20
Purchase #7	$156.99	3.431%	$162.3763	$162.38	$162.40	$162.40
7 purchase totals =	$954.31		$1,031.6288	$1,031.63	$1,031.65	$1,031.70