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	$91.34	5.861%	$96.6934	$96.69	$96.70	$96.70
Purchase #2	$194.32	4.730%	$203.5113	$203.51	$203.50	$203.50
Purchase #3	$186.91	7.266%	$200.4909	$200.49	$200.50	$200.50
Purchase #4	$63.88	11.149%	$71.002	$71.00	$71.00	$71.00
Purchase #5	$89.40	12.691%	$100.7458	$100.75	$100.75	$100.70
Purchase #6	$178.69	12.375%	$200.8029	$200.80	$200.80	$200.80
Purchase #7	$143.49	13.311%	$162.59	$162.59	$162.60	$162.60
7 purchase totals =	$948.03		$1,035.8363	$1,035.83	$1,035.85	$1,035.80