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	$100.87	11.138%	$112.1049	$112.10	$112.10	$112.10
Purchase #2	$59.36	12.373%	$66.7046	$66.70	$66.70	$66.70
Purchase #3	$246.56	3.199%	$254.4475	$254.45	$254.45	$254.40
Purchase #4	$198.89	12.800%	$224.3479	$224.35	$224.35	$224.30
Purchase #5	$45.46	6.254%	$48.3031	$48.30	$48.30	$48.30
Purchase #6	$139.53	9.475%	$152.7505	$152.75	$152.75	$152.80
Purchase #7	$115.30	10.368%	$127.2543	$127.25	$127.25	$127.30
7 purchase totals =	$905.97		$985.9128	$985.90	$985.90	$985.90