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	$132.55	10.846%	$146.9264	$146.93	$146.95	$146.90
Purchase #2	$189.51	3.721%	$196.5617	$196.56	$196.55	$196.60
Purchase #3	$120.86	3.849%	$125.5119	$125.51	$125.50	$125.50
Purchase #4	$76.51	11.419%	$85.2467	$85.25	$85.25	$85.20
Purchase #5	$71.72	13.546%	$81.4352	$81.44	$81.45	$81.40
Purchase #6	$198.89	12.334%	$223.4211	$223.42	$223.40	$223.40
Purchase #7	$210.87	3.318%	$217.8667	$217.87	$217.85	$217.90
7 purchase totals =	$1,000.91		$1,076.9697	$1,076.98	$1,076.95	$1,076.90