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	$10.33	7.173%	$11.071	$11.07	$11.05	$11.10
Purchase #2	$248.98	12.594%	$280.3365	$280.34	$280.35	$280.30
Purchase #3	$89.45	4.224%	$93.2284	$93.23	$93.25	$93.20
Purchase #4	$177.42	4.220%	$184.9071	$184.91	$184.90	$184.90
Purchase #5	$227.38	8.236%	$246.107	$246.11	$246.10	$246.10
Purchase #6	$100.47	8.412%	$108.9215	$108.92	$108.90	$108.90
Purchase #7	$155.54	10.244%	$171.4735	$171.47	$171.45	$171.50
7 purchase totals =	$1,009.57		$1,096.0450	$1,096.05	$1,096.00	$1,096.00