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	$153.89	10.256%	$169.673	$169.67	$169.65	$169.70
Purchase #2	$240.39	9.438%	$263.078	$263.08	$263.10	$263.10
Purchase #3	$89.83	6.466%	$95.6384	$95.64	$95.65	$95.60
Purchase #4	$56.76	13.410%	$64.3715	$64.37	$64.35	$64.40
Purchase #5	$118.34	12.129%	$132.6935	$132.69	$132.70	$132.70
Purchase #6	$104.29	6.744%	$111.3233	$111.32	$111.30	$111.30
Purchase #7	$170.33	8.146%	$184.2051	$184.21	$184.20	$184.20
7 purchase totals =	$933.83		$1,020.9828	$1,020.98	$1,020.95	$1,021.00