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	$167.64	3.708%	$173.8561	$173.86	$173.85	$173.90
Purchase #2	$189.45	6.383%	$201.5426	$201.54	$201.55	$201.50
Purchase #3	$46.27	7.738%	$49.8504	$49.85	$49.85	$49.90
Purchase #4	$90.28	10.504%	$99.763	$99.76	$99.75	$99.80
Purchase #5	$162.42	3.873%	$168.7105	$168.71	$168.70	$168.70
Purchase #6	$128.47	12.576%	$144.6264	$144.63	$144.65	$144.60
Purchase #7	$16.38	11.292%	$18.2296	$18.23	$18.25	$18.20
7 purchase totals =	$800.91		$856.5786	$856.58	$856.60	$856.60