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	$119.43	3.334%	$123.4118	$123.41	$123.40	$123.40
Purchase #2	$91.81	3.779%	$95.2795	$95.28	$95.30	$95.30
Purchase #3	$7.45	5.783%	$7.8808	$7.88	$7.90	$7.90
Purchase #4	$156.65	12.364%	$176.0182	$176.02	$176.00	$176.00
Purchase #5	$68.67	5.438%	$72.4043	$72.40	$72.40	$72.40
Purchase #6	$199.78	5.392%	$210.5521	$210.55	$210.55	$210.60
Purchase #7	$228.96	6.404%	$243.6226	$243.62	$243.60	$243.60
7 purchase totals =	$872.75		$929.1693	$929.16	$929.15	$929.20