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	$129.75	13.361%	$147.0859	$147.09	$147.10	$147.10
Purchase #2	$80.53	7.295%	$86.4047	$86.40	$86.40	$86.40
Purchase #3	$168.57	7.487%	$181.1908	$181.19	$181.20	$181.20
Purchase #4	$132.83	13.561%	$150.8431	$150.84	$150.85	$150.80
Purchase #5	$91.38	11.758%	$102.1245	$102.12	$102.10	$102.10
Purchase #6	$190.89	12.111%	$214.0087	$214.01	$214.00	$214.00
Purchase #7	$63.86	13.519%	$72.4932	$72.49	$72.50	$72.50
7 purchase totals =	$857.81		$954.1509	$954.14	$954.15	$954.10