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	$84.34	3.285%	$87.1106	$87.11	$87.10	$87.10
Purchase #2	$19.46	4.424%	$20.3209	$20.32	$20.30	$20.30
Purchase #3	$121.38	4.679%	$127.0594	$127.06	$127.05	$127.10
Purchase #4	$199.99	12.221%	$224.4308	$224.43	$224.45	$224.40
Purchase #5	$67.51	7.540%	$72.6003	$72.60	$72.60	$72.60
Purchase #6	$110.37	11.814%	$123.4091	$123.41	$123.40	$123.40
Purchase #7	$59.91	8.566%	$65.0419	$65.04	$65.05	$65.00
7 purchase totals =	$662.96		$719.9730	$719.97	$719.95	$719.90