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	$59.86	6.675%	$63.8557	$63.86	$63.85	$63.90
Purchase #2	$72.94	7.594%	$78.4791	$78.48	$78.50	$78.50
Purchase #3	$237.65	7.661%	$255.8564	$255.86	$255.85	$255.90
Purchase #4	$210.53	6.309%	$223.8123	$223.81	$223.80	$223.80
Purchase #5	$126.94	7.248%	$136.1406	$136.14	$136.15	$136.10
Purchase #6	$166.94	10.344%	$184.2083	$184.21	$184.20	$184.20
Purchase #7	$150.36	10.653%	$166.3779	$166.38	$166.40	$166.40
7 purchase totals =	$1,025.22		$1,108.7303	$1,108.74	$1,108.75	$1,108.80