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	$162.73	5.720%	$172.0382	$172.04	$172.05	$172.00
Purchase #2	$104.55	8.180%	$113.1022	$113.10	$113.10	$113.10
Purchase #3	$46.35	13.221%	$52.4779	$52.48	$52.50	$52.50
Purchase #4	$232.53	9.684%	$255.0482	$255.05	$255.05	$255.00
Purchase #5	$89.64	6.302%	$95.2891	$95.29	$95.30	$95.30
Purchase #6	$168.49	10.359%	$185.9439	$185.94	$185.95	$185.90
Purchase #7	$130.50	11.857%	$145.9734	$145.97	$145.95	$146.00
7 purchase totals =	$934.79		$1,019.8729	$1,019.87	$1,019.90	$1,019.80