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	$196.77	7.433%	$211.3959	$211.40	$211.40	$211.40
Purchase #2	$151.94	10.753%	$168.2781	$168.28	$168.30	$168.30
Purchase #3	$196.32	12.482%	$220.8247	$220.82	$220.80	$220.80
Purchase #4	$236.96	4.690%	$248.0734	$248.07	$248.05	$248.10
Purchase #5	$12.55	3.576%	$12.9988	$13.00	$13.00	$13.00
Purchase #6	$129.73	7.514%	$139.4779	$139.48	$139.50	$139.50
Purchase #7	$87.87	8.712%	$95.5252	$95.53	$95.55	$95.50
7 purchase totals =	$1,012.14		$1,096.5740	$1,096.58	$1,096.60	$1,096.60