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	$57.75	12.419%	$64.922	$64.92	$64.90	$64.90
Purchase #2	$157.74	4.562%	$164.9361	$164.94	$164.95	$164.90
Purchase #3	$199.76	9.610%	$218.9569	$218.96	$218.95	$219.00
Purchase #4	$56.59	6.160%	$60.0759	$60.08	$60.10	$60.10
Purchase #5	$205.35	10.874%	$227.6798	$227.68	$227.70	$227.70
Purchase #6	$198.29	5.360%	$208.9183	$208.92	$208.90	$208.90
Purchase #7	$112.39	13.465%	$127.5233	$127.52	$127.50	$127.50
7 purchase totals =	$987.87		$1,073.0123	$1,073.02	$1,073.00	$1,073.00