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	$182.92	9.818%	$200.8791	$200.88	$200.90	$200.90
Purchase #2	$35.64	8.873%	$38.8023	$38.80	$38.80	$38.80
Purchase #3	$167.98	8.597%	$182.4212	$182.42	$182.40	$182.40
Purchase #4	$187.89	12.589%	$211.5435	$211.54	$211.55	$211.50
Purchase #5	$223.65	5.872%	$236.7827	$236.78	$236.80	$236.80
Purchase #6	$61.40	8.340%	$66.5208	$66.52	$66.50	$66.50
Purchase #7	$184.35	12.579%	$207.5394	$207.54	$207.55	$207.50
7 purchase totals =	$1,043.83		$1,144.4890	$1,144.48	$1,144.50	$1,144.40