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	$237.33	10.343%	$261.877	$261.88	$261.90	$261.90
Purchase #2	$133.94	12.663%	$150.9008	$150.90	$150.90	$150.90
Purchase #3	$101.67	10.106%	$111.9448	$111.94	$111.95	$111.90
Purchase #4	$127.75	10.495%	$141.1574	$141.16	$141.15	$141.20
Purchase #5	$236.49	5.430%	$249.3314	$249.33	$249.35	$249.30
Purchase #6	$198.81	12.417%	$223.4962	$223.50	$223.50	$223.50
Purchase #7	$9.88	12.108%	$11.0763	$11.08	$11.10	$11.10
7 purchase totals =	$1,045.87		$1,149.7839	$1,149.79	$1,149.85	$1,149.80