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	$105.43	3.549%	$109.1717	$109.17	$109.15	$109.20
Purchase #2	$40.44	8.545%	$43.8956	$43.90	$43.90	$43.90
Purchase #3	$178.31	6.489%	$189.8805	$189.88	$189.90	$189.90
Purchase #4	$250.38	13.376%	$283.8708	$283.87	$283.85	$283.90
Purchase #5	$134.44	3.225%	$138.7757	$138.78	$138.80	$138.80
Purchase #6	$50.74	11.695%	$56.674	$56.67	$56.65	$56.70
Purchase #7	$173.32	7.121%	$185.6621	$185.66	$185.65	$185.70
7 purchase totals =	$933.06		$1,007.9304	$1,007.93	$1,007.90	$1,008.10