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	$168.32	9.700%	$184.647	$184.65	$184.65	$184.60
Purchase #2	$234.84	12.735%	$264.7469	$264.75	$264.75	$264.70
Purchase #3	$36.37	9.587%	$39.8568	$39.86	$39.85	$39.90
Purchase #4	$6.85	12.518%	$7.7075	$7.71	$7.70	$7.70
Purchase #5	$57.76	5.443%	$60.9039	$60.90	$60.90	$60.90
Purchase #6	$34.96	7.570%	$37.6065	$37.61	$37.60	$37.60
Purchase #7	$115.59	3.387%	$119.505	$119.51	$119.50	$119.50
7 purchase totals =	$654.69		$714.9736	$714.99	$714.95	$714.90