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	$187.67	11.112%	$208.5239	$208.52	$208.50	$208.50
Purchase #2	$133.49	10.320%	$147.2662	$147.27	$147.25	$147.30
Purchase #3	$78.41	10.309%	$86.4933	$86.49	$86.50	$86.50
Purchase #4	$106.49	3.331%	$110.0372	$110.04	$110.05	$110.00
Purchase #5	$189.75	5.715%	$200.5942	$200.59	$200.60	$200.60
Purchase #6	$18.59	8.664%	$20.2006	$20.20	$20.20	$20.20
Purchase #7	$134.89	13.187%	$152.6779	$152.68	$152.70	$152.70
7 purchase totals =	$849.29		$925.7933	$925.79	$925.80	$925.80