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	$69.63	10.429%	$76.8917	$76.89	$76.90	$76.90
Purchase #2	$104.82	12.368%	$117.7841	$117.78	$117.80	$117.80
Purchase #3	$31.74	5.256%	$33.4083	$33.41	$33.40	$33.40
Purchase #4	$157.31	13.661%	$178.8001	$178.80	$178.80	$178.80
Purchase #5	$247.59	13.387%	$280.7349	$280.73	$280.75	$280.70
Purchase #6	$219.70	9.672%	$240.9494	$240.95	$240.95	$240.90
Purchase #7	$176.55	3.467%	$182.671	$182.67	$182.65	$182.70
7 purchase totals =	$1,007.34		$1,111.2395	$1,111.23	$1,111.25	$1,111.20