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	$10.29	11.170%	$11.4394	$11.44	$11.45	$11.40
Purchase #2	$138.61	9.817%	$152.2173	$152.22	$152.20	$152.20
Purchase #3	$110.35	7.276%	$118.3791	$118.38	$118.40	$118.40
Purchase #4	$64.93	8.541%	$70.4757	$70.48	$70.50	$70.50
Purchase #5	$90.67	9.687%	$99.4532	$99.45	$99.45	$99.50
Purchase #6	$143.68	6.732%	$153.3525	$153.35	$153.35	$153.40
Purchase #7	$164.79	10.751%	$182.5066	$182.51	$182.50	$182.50
7 purchase totals =	$723.32		$787.8238	$787.83	$787.85	$787.90