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	$35.34	9.810%	$38.8069	$38.81	$38.80	$38.80
Purchase #2	$247.51	13.259%	$280.3274	$280.33	$280.35	$280.30
Purchase #3	$81.72	4.349%	$85.274	$85.27	$85.25	$85.30
Purchase #4	$193.50	3.823%	$200.8975	$200.90	$200.90	$200.90
Purchase #5	$144.30	4.125%	$150.2524	$150.25	$150.25	$150.30
Purchase #6	$232.56	4.333%	$242.6368	$242.64	$242.65	$242.60
Purchase #7	$30.80	11.162%	$34.2379	$34.24	$34.25	$34.20
7 purchase totals =	$965.73		$1,032.4329	$1,032.44	$1,032.45	$1,032.40