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	$24.55	7.742%	$26.4507	$26.45	$26.45	$26.50
Purchase #2	$182.89	9.403%	$200.0871	$200.09	$200.10	$200.10
Purchase #3	$222.27	12.864%	$250.8628	$250.86	$250.85	$250.90
Purchase #4	$149.54	3.781%	$155.1941	$155.19	$155.20	$155.20
Purchase #5	$132.97	13.286%	$150.6364	$150.64	$150.65	$150.60
Purchase #6	$109.38	13.121%	$123.7317	$123.73	$123.75	$123.70
Purchase #7	$136.76	7.686%	$147.2714	$147.27	$147.25	$147.30
7 purchase totals =	$958.36		$1,054.2342	$1,054.23	$1,054.25	$1,054.30