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	$146.79	13.415%	$166.4819	$166.48	$166.50	$166.50
Purchase #2	$199.51	12.514%	$224.4767	$224.48	$224.50	$224.50
Purchase #3	$53.25	12.399%	$59.8525	$59.85	$59.85	$59.90
Purchase #4	$198.77	7.593%	$213.8626	$213.86	$213.85	$213.90
Purchase #5	$247.66	13.389%	$280.8192	$280.82	$280.80	$280.80
Purchase #6	$173.74	13.333%	$196.9048	$196.90	$196.90	$196.90
Purchase #7	$88.62	5.735%	$93.7024	$93.70	$93.70	$93.70
7 purchase totals =	$1,108.34		$1,236.1001	$1,236.09	$1,236.10	$1,236.20