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	$218.43	10.332%	$240.9982	$241.00	$241.00	$241.00
Purchase #2	$136.34	10.279%	$150.3544	$150.35	$150.35	$150.40
Purchase #3	$112.88	13.867%	$128.5331	$128.53	$128.55	$128.50
Purchase #4	$152.54	8.812%	$165.9818	$165.98	$166.00	$166.00
Purchase #5	$119.63	6.382%	$127.2648	$127.26	$127.25	$127.30
Purchase #6	$142.58	3.398%	$147.4249	$147.42	$147.40	$147.40
Purchase #7	$90.40	7.757%	$97.4123	$97.41	$97.40	$97.40
7 purchase totals =	$972.80		$1,057.9695	$1,057.95	$1,057.95	$1,058.00