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	$100.27	4.330%	$104.6117	$104.61	$104.60	$104.60
Purchase #2	$145.61	5.102%	$153.039	$153.04	$153.05	$153.00
Purchase #3	$158.32	8.872%	$172.3662	$172.37	$172.35	$172.40
Purchase #4	$186.99	9.279%	$204.3408	$204.34	$204.35	$204.30
Purchase #5	$140.27	11.729%	$156.7223	$156.72	$156.70	$156.70
Purchase #6	$44.58	4.432%	$46.5558	$46.56	$46.55	$46.60
Purchase #7	$71.94	8.755%	$78.2383	$78.24	$78.25	$78.20
7 purchase totals =	$847.98		$915.8741	$915.88	$915.85	$915.80