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	$165.31	9.126%	$180.3962	$180.40	$180.40	$180.40
Purchase #2	$212.28	4.849%	$222.5735	$222.57	$222.55	$222.60
Purchase #3	$56.46	5.178%	$59.3835	$59.38	$59.40	$59.40
Purchase #4	$81.73	5.862%	$86.521	$86.52	$86.50	$86.50
Purchase #5	$190.85	9.498%	$208.9769	$208.98	$209.00	$209.00
Purchase #6	$26.78	7.709%	$28.8445	$28.84	$28.85	$28.80
Purchase #7	$115.52	5.839%	$122.2652	$122.27	$122.25	$122.30
7 purchase totals =	$848.93		$908.9608	$908.96	$908.95	$909.00