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	$162.45	5.546%	$171.4595	$171.46	$171.45	$171.50
Purchase #2	$35.31	9.527%	$38.674	$38.67	$38.65	$38.70
Purchase #3	$167.72	4.590%	$175.4183	$175.42	$175.40	$175.40
Purchase #4	$72.49	7.518%	$77.9398	$77.94	$77.95	$77.90
Purchase #5	$199.68	9.371%	$218.392	$218.39	$218.40	$218.40
Purchase #6	$53.41	9.256%	$58.3536	$58.35	$58.35	$58.40
Purchase #7	$112.82	9.442%	$123.4725	$123.47	$123.45	$123.50
7 purchase totals =	$803.88		$863.7097	$863.70	$863.65	$863.80