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	$154.42	4.182%	$160.8778	$160.88	$160.90	$160.90
Purchase #2	$132.48	7.142%	$141.9417	$141.94	$141.95	$141.90
Purchase #3	$99.88	5.512%	$105.3854	$105.39	$105.40	$105.40
Purchase #4	$176.25	3.619%	$182.6285	$182.63	$182.65	$182.60
Purchase #5	$232.42	12.642%	$261.8025	$261.80	$261.80	$261.80
Purchase #6	$154.39	11.176%	$171.6446	$171.64	$171.65	$171.60
Purchase #7	$249.25	11.259%	$277.3131	$277.31	$277.30	$277.30
7 purchase totals =	$1,199.09		$1,301.5936	$1,301.59	$1,301.65	$1,301.50