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	$224.68	10.796%	$248.9365	$248.94	$248.95	$248.90
Purchase #2	$117.35	13.403%	$133.0784	$133.08	$133.10	$133.10
Purchase #3	$146.86	3.756%	$152.3761	$152.38	$152.40	$152.40
Purchase #4	$37.82	11.508%	$42.1723	$42.17	$42.15	$42.20
Purchase #5	$234.51	12.768%	$264.4522	$264.45	$264.45	$264.50
Purchase #6	$214.43	4.717%	$224.5447	$224.54	$224.55	$224.50
Purchase #7	$31.38	11.703%	$35.0524	$35.05	$35.05	$35.10
7 purchase totals =	$1,007.03		$1,100.6126	$1,100.61	$1,100.65	$1,100.70