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	$131.79	10.661%	$145.8401	$145.84	$145.85	$145.80
Purchase #2	$138.39	4.741%	$144.9511	$144.95	$144.95	$145.00
Purchase #3	$205.48	10.265%	$226.5725	$226.57	$226.55	$226.60
Purchase #4	$200.57	11.607%	$223.8502	$223.85	$223.85	$223.90
Purchase #5	$81.93	5.150%	$86.1494	$86.15	$86.15	$86.10
Purchase #6	$133.79	4.451%	$139.745	$139.75	$139.75	$139.70
Purchase #7	$49.29	7.663%	$53.0671	$53.07	$53.05	$53.10
7 purchase totals =	$941.24		$1,020.1754	$1,020.18	$1,020.15	$1,020.20