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	$245.85	5.578%	$259.5635	$259.56	$259.55	$259.60
Purchase #2	$181.58	8.177%	$196.4278	$196.43	$196.45	$196.40
Purchase #3	$149.76	9.664%	$164.2328	$164.23	$164.25	$164.20
Purchase #4	$144.46	13.599%	$164.1051	$164.11	$164.10	$164.10
Purchase #5	$32.74	5.618%	$34.5793	$34.58	$34.60	$34.60
Purchase #6	$144.60	12.586%	$162.7994	$162.80	$162.80	$162.80
Purchase #7	$94.69	7.793%	$102.0692	$102.07	$102.05	$102.10
7 purchase totals =	$993.68		$1,083.7771	$1,083.78	$1,083.80	$1,083.80