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	$171.90	9.869%	$188.8648	$188.86	$188.85	$188.90
Purchase #2	$23.64	9.370%	$25.8551	$25.86	$25.85	$25.90
Purchase #3	$59.95	9.865%	$65.8641	$65.86	$65.85	$65.90
Purchase #4	$188.27	12.839%	$212.442	$212.44	$212.45	$212.40
Purchase #5	$162.98	10.146%	$179.516	$179.52	$179.50	$179.50
Purchase #6	$178.40	6.306%	$189.6499	$189.65	$189.65	$189.60
Purchase #7	$198.35	5.258%	$208.7792	$208.78	$208.80	$208.80
7 purchase totals =	$983.49		$1,070.9711	$1,070.97	$1,070.95	$1,071.00