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	$103.99	9.666%	$114.0417	$114.04	$114.05	$114.00
Purchase #2	$70.70	11.126%	$78.5661	$78.57	$78.55	$78.60
Purchase #3	$250.81	7.290%	$269.094	$269.09	$269.10	$269.10
Purchase #4	$110.96	6.449%	$118.1158	$118.12	$118.10	$118.10
Purchase #5	$152.27	10.829%	$168.7593	$168.76	$168.75	$168.80
Purchase #6	$247.47	13.171%	$280.0643	$280.06	$280.05	$280.10
Purchase #7	$82.57	9.396%	$90.3283	$90.33	$90.35	$90.30
7 purchase totals =	$1,018.77		$1,118.9695	$1,118.97	$1,118.95	$1,119.00