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	$151.86	8.262%	$164.4067	$164.41	$164.40	$164.40
Purchase #2	$249.57	10.480%	$275.7249	$275.72	$275.70	$275.70
Purchase #3	$158.88	4.351%	$165.7929	$165.79	$165.80	$165.80
Purchase #4	$5.32	13.768%	$6.0525	$6.05	$6.05	$6.10
Purchase #5	$84.32	12.214%	$94.6188	$94.62	$94.60	$94.60
Purchase #6	$187.88	6.639%	$200.3534	$200.35	$200.35	$200.40
Purchase #7	$161.77	7.210%	$173.4336	$173.43	$173.45	$173.40
7 purchase totals =	$999.60		$1,080.3828	$1,080.37	$1,080.35	$1,080.40