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	$18.80	4.544%	$19.6543	$19.65	$19.65	$19.70
Purchase #2	$45.56	11.801%	$50.9365	$50.94	$50.95	$50.90
Purchase #3	$125.80	4.712%	$131.7277	$131.73	$131.75	$131.70
Purchase #4	$73.79	11.367%	$82.1777	$82.18	$82.20	$82.20
Purchase #5	$246.86	3.656%	$255.8852	$255.89	$255.90	$255.90
Purchase #6	$46.32	12.528%	$52.123	$52.12	$52.10	$52.10
Purchase #7	$248.75	9.769%	$273.0504	$273.05	$273.05	$273.10
7 purchase totals =	$805.88		$865.5548	$865.56	$865.60	$865.60