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	$64.27	11.410%	$71.6032	$71.60	$71.60	$71.60
Purchase #2	$160.27	8.691%	$174.1991	$174.20	$174.20	$174.20
Purchase #3	$50.84	4.854%	$53.3078	$53.31	$53.30	$53.30
Purchase #4	$175.33	7.140%	$187.8486	$187.85	$187.85	$187.80
Purchase #5	$214.29	3.340%	$221.4473	$221.45	$221.45	$221.40
Purchase #6	$50.61	4.439%	$52.8566	$52.86	$52.85	$52.90
Purchase #7	$168.35	12.327%	$189.1025	$189.10	$189.10	$189.10
7 purchase totals =	$883.96		$950.3651	$950.37	$950.35	$950.30