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	$92.86	8.573%	$100.8209	$100.82	$100.80	$100.80
Purchase #2	$83.99	8.828%	$91.4046	$91.40	$91.40	$91.40
Purchase #3	$243.29	6.426%	$258.9238	$258.92	$258.90	$258.90
Purchase #4	$163.53	9.410%	$178.9182	$178.92	$178.90	$178.90
Purchase #5	$63.43	13.633%	$72.0774	$72.08	$72.10	$72.10
Purchase #6	$126.92	9.795%	$139.3518	$139.35	$139.35	$139.40
Purchase #7	$43.52	7.150%	$46.6317	$46.63	$46.65	$46.60
7 purchase totals =	$817.54		$888.1284	$888.12	$888.10	$888.10