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	$98.25	11.120%	$109.1754	$109.18	$109.20	$109.20
Purchase #2	$218.50	10.276%	$240.9531	$240.95	$240.95	$241.00
Purchase #3	$111.51	5.655%	$117.8159	$117.82	$117.80	$117.80
Purchase #4	$19.42	5.195%	$20.4289	$20.43	$20.45	$20.40
Purchase #5	$200.65	6.163%	$213.0161	$213.02	$213.00	$213.00
Purchase #6	$72.36	6.756%	$77.2486	$77.25	$77.25	$77.20
Purchase #7	$104.84	6.661%	$111.8234	$111.82	$111.80	$111.80
7 purchase totals =	$825.53		$890.4614	$890.47	$890.45	$890.40