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	$72.98	10.475%	$80.6247	$80.62	$80.60	$80.60
Purchase #2	$67.40	6.221%	$71.593	$71.59	$71.60	$71.60
Purchase #3	$172.52	11.120%	$191.7042	$191.70	$191.70	$191.70
Purchase #4	$33.90	8.287%	$36.7093	$36.71	$36.70	$36.70
Purchase #5	$119.58	10.180%	$131.7532	$131.75	$131.75	$131.80
Purchase #6	$249.61	12.486%	$280.7763	$280.78	$280.80	$280.80
Purchase #7	$66.79	13.597%	$75.8714	$75.87	$75.85	$75.90
7 purchase totals =	$782.78		$869.0321	$869.02	$869.00	$869.10