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	$244.84	5.835%	$259.1264	$259.13	$259.15	$259.10
Purchase #2	$114.99	9.141%	$125.5012	$125.50	$125.50	$125.50
Purchase #3	$94.28	6.410%	$100.3233	$100.32	$100.30	$100.30
Purchase #4	$90.79	9.379%	$99.3052	$99.31	$99.30	$99.30
Purchase #5	$225.99	6.788%	$241.3302	$241.33	$241.35	$241.30
Purchase #6	$63.46	11.769%	$70.9286	$70.93	$70.95	$70.90
Purchase #7	$92.66	12.280%	$104.0386	$104.04	$104.05	$104.00
7 purchase totals =	$927.01		$1,000.5535	$1,000.56	$1,000.60	$1,000.40