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	$145.72	4.463%	$152.2235	$152.22	$152.20	$152.20
Purchase #2	$123.86	11.174%	$137.7001	$137.70	$137.70	$137.70
Purchase #3	$249.78	9.664%	$273.9187	$273.92	$273.90	$273.90
Purchase #4	$58.42	6.207%	$62.0461	$62.05	$62.05	$62.00
Purchase #5	$69.77	9.181%	$76.1756	$76.18	$76.20	$76.20
Purchase #6	$246.95	13.679%	$280.7303	$280.73	$280.75	$280.70
Purchase #7	$37.90	12.189%	$42.5196	$42.52	$42.50	$42.50
7 purchase totals =	$932.40		$1,025.3139	$1,025.32	$1,025.30	$1,025.20