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	$206.96	13.221%	$234.3222	$234.32	$234.30	$234.30
Purchase #2	$82.68	4.607%	$86.4891	$86.49	$86.50	$86.50
Purchase #3	$179.92	11.661%	$200.9005	$200.90	$200.90	$200.90
Purchase #4	$208.63	10.354%	$230.2316	$230.23	$230.25	$230.20
Purchase #5	$91.59	8.157%	$99.061	$99.06	$99.05	$99.10
Purchase #6	$43.99	13.496%	$49.9269	$49.93	$49.95	$49.90
Purchase #7	$125.50	8.768%	$136.5038	$136.50	$136.50	$136.50
7 purchase totals =	$939.27		$1,037.4351	$1,037.43	$1,037.45	$1,037.40