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	$93.47	11.341%	$104.0704	$104.07	$104.05	$104.10
Purchase #2	$92.85	3.301%	$95.915	$95.92	$95.90	$95.90
Purchase #3	$249.58	8.211%	$270.073	$270.07	$270.05	$270.10
Purchase #4	$117.85	11.190%	$131.0374	$131.04	$131.05	$131.00
Purchase #5	$200.56	6.568%	$213.7328	$213.73	$213.75	$213.70
Purchase #6	$127.42	11.348%	$141.8796	$141.88	$141.90	$141.90
Purchase #7	$166.54	13.834%	$189.5791	$189.58	$189.60	$189.60
7 purchase totals =	$1,048.27		$1,146.2873	$1,146.29	$1,146.30	$1,146.30