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	$61.86	4.330%	$64.5385	$64.54	$64.55	$64.50
Purchase #2	$82.40	13.569%	$93.5809	$93.58	$93.60	$93.60
Purchase #3	$78.39	13.390%	$88.8864	$88.89	$88.90	$88.90
Purchase #4	$227.52	9.816%	$249.8534	$249.85	$249.85	$249.90
Purchase #5	$191.58	7.166%	$205.3086	$205.31	$205.30	$205.30
Purchase #6	$241.35	3.552%	$249.9228	$249.92	$249.90	$249.90
Purchase #7	$146.90	4.473%	$153.4708	$153.47	$153.45	$153.50
7 purchase totals =	$1,030.00		$1,105.5614	$1,105.56	$1,105.55	$1,105.60