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	$245.37	13.764%	$279.1427	$279.14	$279.15	$279.10
Purchase #2	$34.67	6.475%	$36.9149	$36.91	$36.90	$36.90
Purchase #3	$88.90	7.556%	$95.6173	$95.62	$95.60	$95.60
Purchase #4	$145.68	6.623%	$155.3284	$155.33	$155.35	$155.30
Purchase #5	$239.51	7.277%	$256.9391	$256.94	$256.95	$256.90
Purchase #6	$12.52	5.275%	$13.1804	$13.18	$13.20	$13.20
Purchase #7	$150.52	9.138%	$164.2745	$164.27	$164.25	$164.30
7 purchase totals =	$917.17		$1,001.3973	$1,001.39	$1,001.40	$1,001.30