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	$137.47	7.802%	$148.1954	$148.20	$148.20	$148.20
Purchase #2	$206.38	7.811%	$222.5003	$222.50	$222.50	$222.50
Purchase #3	$48.42	7.404%	$52.005	$52.01	$52.00	$52.00
Purchase #4	$127.36	3.497%	$131.8138	$131.81	$131.80	$131.80
Purchase #5	$139.36	8.528%	$151.2446	$151.24	$151.25	$151.20
Purchase #6	$200.35	9.706%	$219.796	$219.80	$219.80	$219.80
Purchase #7	$234.36	9.218%	$255.9633	$255.96	$255.95	$256.00
7 purchase totals =	$1,093.70		$1,181.5184	$1,181.52	$1,181.50	$1,181.50