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	$232.78	4.725%	$243.7789	$243.78	$243.80	$243.80
Purchase #2	$114.25	4.563%	$119.4632	$119.46	$119.45	$119.50
Purchase #3	$111.37	10.290%	$122.83	$122.83	$122.85	$122.80
Purchase #4	$159.68	12.172%	$179.1162	$179.12	$179.10	$179.10
Purchase #5	$216.80	11.380%	$241.4718	$241.47	$241.45	$241.50
Purchase #6	$75.92	6.269%	$80.6794	$80.68	$80.70	$80.70
Purchase #7	$20.35	10.480%	$22.4827	$22.48	$22.50	$22.50
7 purchase totals =	$931.15		$1,009.8222	$1,009.82	$1,009.85	$1,009.90