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	$78.58	4.789%	$82.3432	$82.34	$82.35	$82.30
Purchase #2	$56.58	5.874%	$59.9035	$59.90	$59.90	$59.90
Purchase #3	$88.95	9.237%	$97.1663	$97.17	$97.15	$97.20
Purchase #4	$79.92	8.474%	$86.6924	$86.69	$86.70	$86.70
Purchase #5	$126.36	6.181%	$134.1703	$134.17	$134.15	$134.20
Purchase #6	$203.82	9.372%	$222.922	$222.92	$222.90	$222.90
Purchase #7	$61.62	12.720%	$69.4581	$69.46	$69.45	$69.50
7 purchase totals =	$695.83		$752.6558	$752.65	$752.60	$752.70