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	$146.85	12.590%	$165.3384	$165.34	$165.35	$165.30
Purchase #2	$87.48	13.481%	$99.2732	$99.27	$99.25	$99.30
Purchase #3	$222.50	11.678%	$248.4836	$248.48	$248.50	$248.50
Purchase #4	$186.85	8.520%	$202.7696	$202.77	$202.75	$202.80
Purchase #5	$85.89	7.777%	$92.5697	$92.57	$92.55	$92.60
Purchase #6	$94.58	3.695%	$98.0747	$98.07	$98.05	$98.10
Purchase #7	$89.29	12.772%	$100.6941	$100.69	$100.70	$100.70
7 purchase totals =	$913.44		$1,007.2033	$1,007.19	$1,007.15	$1,007.30