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	$33.39	5.489%	$35.2228	$35.22	$35.20	$35.20
Purchase #2	$89.46	5.443%	$94.3293	$94.33	$94.35	$94.30
Purchase #3	$90.99	4.167%	$94.7816	$94.78	$94.80	$94.80
Purchase #4	$94.60	8.353%	$102.5019	$102.50	$102.50	$102.50
Purchase #5	$237.63	5.459%	$250.6022	$250.60	$250.60	$250.60
Purchase #6	$113.25	8.669%	$123.0676	$123.07	$123.05	$123.10
Purchase #7	$223.45	4.442%	$233.3756	$233.38	$233.40	$233.40
7 purchase totals =	$882.77		$933.8810	$933.88	$933.90	$933.90