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	$204.42	8.700%	$222.2045	$222.20	$222.20	$222.20
Purchase #2	$109.72	3.227%	$113.2607	$113.26	$113.25	$113.30
Purchase #3	$30.30	8.348%	$32.8294	$32.83	$32.85	$32.80
Purchase #4	$226.78	13.873%	$258.2412	$258.24	$258.25	$258.20
Purchase #5	$210.79	11.497%	$235.0245	$235.02	$235.00	$235.00
Purchase #6	$75.86	9.836%	$83.3216	$83.32	$83.30	$83.30
Purchase #7	$181.71	10.284%	$200.3971	$200.40	$200.40	$200.40
7 purchase totals =	$1,039.58		$1,145.2790	$1,145.27	$1,145.25	$1,145.20