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	$198.76	13.321%	$225.2368	$225.24	$225.25	$225.20
Purchase #2	$41.95	8.330%	$45.4444	$45.44	$45.45	$45.40
Purchase #3	$110.87	13.102%	$125.3962	$125.40	$125.40	$125.40
Purchase #4	$239.80	4.318%	$250.1546	$250.15	$250.15	$250.20
Purchase #5	$215.84	10.300%	$238.0715	$238.07	$238.05	$238.10
Purchase #6	$98.67	12.850%	$111.3491	$111.35	$111.35	$111.30
Purchase #7	$241.36	10.390%	$266.4373	$266.44	$266.45	$266.40
7 purchase totals =	$1,147.25		$1,262.0899	$1,262.09	$1,262.10	$1,262.00