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	$167.54	10.868%	$185.7482	$185.75	$185.75	$185.70
Purchase #2	$17.99	13.381%	$20.3972	$20.40	$20.40	$20.40
Purchase #3	$93.31	6.452%	$99.3304	$99.33	$99.35	$99.30
Purchase #4	$87.61	10.777%	$97.0517	$97.05	$97.05	$97.10
Purchase #5	$82.53	3.738%	$85.615	$85.62	$85.60	$85.60
Purchase #6	$191.49	11.536%	$213.5803	$213.58	$213.60	$213.60
Purchase #7	$79.60	7.867%	$85.8621	$85.86	$85.85	$85.90
7 purchase totals =	$720.07		$787.5849	$787.59	$787.60	$787.60