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	$248.45	7.709%	$267.603	$267.60	$267.60	$267.60
Purchase #2	$210.71	7.634%	$226.7956	$226.80	$226.80	$226.80
Purchase #3	$130.79	8.378%	$141.7476	$141.75	$141.75	$141.70
Purchase #4	$187.98	4.640%	$196.7023	$196.70	$196.70	$196.70
Purchase #5	$191.58	4.688%	$200.5613	$200.56	$200.55	$200.60
Purchase #6	$229.51	3.854%	$238.3553	$238.36	$238.35	$238.40
Purchase #7	$112.38	13.623%	$127.6895	$127.69	$127.70	$127.70
7 purchase totals =	$1,311.40		$1,399.4546	$1,399.46	$1,399.45	$1,399.50