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	$205.40	5.590%	$216.8819	$216.88	$216.90	$216.90
Purchase #2	$228.59	13.686%	$259.8748	$259.87	$259.85	$259.90
Purchase #3	$74.81	8.199%	$80.9437	$80.94	$80.95	$80.90
Purchase #4	$41.32	9.655%	$45.3094	$45.31	$45.30	$45.30
Purchase #5	$227.81	3.648%	$236.1205	$236.12	$236.10	$236.10
Purchase #6	$238.95	5.167%	$251.2965	$251.30	$251.30	$251.30
Purchase #7	$88.76	13.565%	$100.8003	$100.80	$100.80	$100.80
7 purchase totals =	$1,105.64		$1,191.2271	$1,191.22	$1,191.20	$1,191.20