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	$217.28	6.473%	$231.3445	$231.34	$231.35	$231.30
Purchase #2	$108.90	6.869%	$116.3803	$116.38	$116.40	$116.40
Purchase #3	$105.64	7.417%	$113.4753	$113.48	$113.50	$113.50
Purchase #4	$177.44	10.497%	$196.0659	$196.07	$196.05	$196.10
Purchase #5	$102.76	9.553%	$112.5767	$112.58	$112.60	$112.60
Purchase #6	$244.94	10.104%	$269.6887	$269.69	$269.70	$269.70
Purchase #7	$25.78	5.607%	$27.2255	$27.23	$27.25	$27.20
7 purchase totals =	$982.74		$1,066.7569	$1,066.77	$1,066.85	$1,066.80