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	$148.58	3.572%	$153.8873	$153.89	$153.90	$153.90
Purchase #2	$25.35	6.720%	$27.0535	$27.05	$27.05	$27.10
Purchase #3	$147.35	12.333%	$165.5227	$165.52	$165.50	$165.50
Purchase #4	$207.76	12.450%	$233.6261	$233.63	$233.65	$233.60
Purchase #5	$84.25	7.365%	$90.455	$90.46	$90.45	$90.50
Purchase #6	$103.67	8.855%	$112.85	$112.85	$112.85	$112.90
Purchase #7	$95.52	5.274%	$100.5577	$100.56	$100.55	$100.60
7 purchase totals =	$812.48		$883.9523	$883.96	$883.95	$884.10