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	$150.29	9.365%	$164.3647	$164.36	$164.35	$164.40
Purchase #2	$203.35	10.311%	$224.3174	$224.32	$224.30	$224.30
Purchase #3	$144.67	12.583%	$162.8738	$162.87	$162.85	$162.90
Purchase #4	$90.40	8.175%	$97.7902	$97.79	$97.80	$97.80
Purchase #5	$159.56	3.310%	$164.8414	$164.84	$164.85	$164.80
Purchase #6	$167.89	3.566%	$173.877	$173.88	$173.90	$173.90
Purchase #7	$114.53	11.424%	$127.6139	$127.61	$127.60	$127.60
7 purchase totals =	$1,030.69		$1,115.6784	$1,115.67	$1,115.65	$1,115.70