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	$178.65	9.328%	$195.3145	$195.31	$195.30	$195.30
Purchase #2	$13.36	3.859%	$13.8756	$13.88	$13.90	$13.90
Purchase #3	$164.55	6.313%	$174.938	$174.94	$174.95	$174.90
Purchase #4	$171.41	11.140%	$190.5051	$190.51	$190.50	$190.50
Purchase #5	$72.95	4.476%	$76.2152	$76.22	$76.20	$76.20
Purchase #6	$113.75	8.735%	$123.6861	$123.69	$123.70	$123.70
Purchase #7	$42.69	5.647%	$45.1007	$45.10	$45.10	$45.10
7 purchase totals =	$757.36		$819.6352	$819.65	$819.65	$819.60