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	$107.28	6.687%	$114.4538	$114.45	$114.45	$114.50
Purchase #2	$79.25	7.284%	$85.0226	$85.02	$85.00	$85.00
Purchase #3	$88.53	12.356%	$99.4688	$99.47	$99.45	$99.50
Purchase #4	$94.58	6.659%	$100.8781	$100.88	$100.90	$100.90
Purchase #5	$108.54	8.114%	$117.3469	$117.35	$117.35	$117.30
Purchase #6	$128.97	12.236%	$144.7508	$144.75	$144.75	$144.80
Purchase #7	$10.34	5.216%	$10.8793	$10.88	$10.90	$10.90
7 purchase totals =	$617.49		$672.8003	$672.80	$672.80	$672.90