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	$75.53	8.756%	$82.1434	$82.14	$82.15	$82.10
Purchase #2	$89.53	6.633%	$95.4685	$95.47	$95.45	$95.50
Purchase #3	$184.87	6.114%	$196.173	$196.17	$196.15	$196.20
Purchase #4	$84.57	10.709%	$93.6266	$93.63	$93.65	$93.60
Purchase #5	$48.70	5.787%	$51.5183	$51.52	$51.50	$51.50
Purchase #6	$6.51	7.180%	$6.9774	$6.98	$7.00	$7.00
Purchase #7	$217.82	9.512%	$238.539	$238.54	$238.55	$238.50
7 purchase totals =	$707.53		$764.4462	$764.45	$764.45	$764.40