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	$236.83	11.744%	$264.6433	$264.64	$264.65	$264.60
Purchase #2	$41.49	11.487%	$46.256	$46.26	$46.25	$46.30
Purchase #3	$24.41	12.579%	$27.4805	$27.48	$27.50	$27.50
Purchase #4	$29.82	7.739%	$32.1278	$32.13	$32.15	$32.10
Purchase #5	$31.49	6.166%	$33.4317	$33.43	$33.45	$33.40
Purchase #6	$202.77	5.663%	$214.2529	$214.25	$214.25	$214.30
Purchase #7	$82.77	6.746%	$88.3537	$88.35	$88.35	$88.40
7 purchase totals =	$649.58		$706.5459	$706.54	$706.60	$706.60