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	$210.45	9.817%	$231.1099	$231.11	$231.10	$231.10
Purchase #2	$72.97	7.205%	$78.2275	$78.23	$78.25	$78.20
Purchase #3	$121.34	5.126%	$127.5599	$127.56	$127.55	$127.60
Purchase #4	$210.78	7.643%	$226.8899	$226.89	$226.90	$226.90
Purchase #5	$171.94	8.331%	$186.2643	$186.26	$186.25	$186.30
Purchase #6	$26.70	7.743%	$28.7674	$28.77	$28.75	$28.80
Purchase #7	$175.70	11.672%	$196.2077	$196.21	$196.20	$196.20
7 purchase totals =	$989.88		$1,075.0266	$1,075.03	$1,075.00	$1,075.10