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	$141.36	9.221%	$154.3948	$154.39	$154.40	$154.40
Purchase #2	$104.31	5.323%	$109.8624	$109.86	$109.85	$109.90
Purchase #3	$124.82	11.141%	$138.7262	$138.73	$138.75	$138.70
Purchase #4	$94.90	4.821%	$99.4751	$99.48	$99.50	$99.50
Purchase #5	$18.64	12.540%	$20.9775	$20.98	$21.00	$21.00
Purchase #6	$88.97	9.678%	$97.5805	$97.58	$97.60	$97.60
Purchase #7	$219.35	4.154%	$228.4618	$228.46	$228.45	$228.50
7 purchase totals =	$792.35		$849.4783	$849.48	$849.55	$849.60