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	$110.34	7.517%	$118.6343	$118.63	$118.65	$118.60
Purchase #2	$216.72	9.829%	$238.0214	$238.02	$238.00	$238.00
Purchase #3	$164.88	10.413%	$182.049	$182.05	$182.05	$182.00
Purchase #4	$114.31	6.377%	$121.5995	$121.60	$121.60	$121.60
Purchase #5	$153.29	8.108%	$165.7188	$165.72	$165.70	$165.70
Purchase #6	$132.37	5.817%	$140.07	$140.07	$140.05	$140.10
Purchase #7	$92.96	7.665%	$100.0854	$100.09	$100.10	$100.10
7 purchase totals =	$984.87		$1,066.1784	$1,066.18	$1,066.15	$1,066.10