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	$119.48	6.770%	$127.5688	$127.57	$127.55	$127.60
Purchase #2	$239.56	10.666%	$265.1115	$265.11	$265.10	$265.10
Purchase #3	$56.90	4.504%	$59.4628	$59.46	$59.45	$59.50
Purchase #4	$127.38	9.709%	$139.7473	$139.75	$139.75	$139.70
Purchase #5	$135.32	9.413%	$148.0577	$148.06	$148.05	$148.10
Purchase #6	$160.55	10.245%	$176.9983	$177.00	$177.00	$177.00
Purchase #7	$69.50	11.723%	$77.6475	$77.65	$77.65	$77.60
7 purchase totals =	$908.69		$994.5939	$994.60	$994.55	$994.60