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	$191.30	10.271%	$210.9484	$210.95	$210.95	$210.90
Purchase #2	$41.28	3.710%	$42.8115	$42.81	$42.80	$42.80
Purchase #3	$53.59	7.835%	$57.7888	$57.79	$57.80	$57.80
Purchase #4	$78.33	10.450%	$86.5155	$86.52	$86.50	$86.50
Purchase #5	$6.89	9.141%	$7.5198	$7.52	$7.50	$7.50
Purchase #6	$152.87	3.241%	$157.8245	$157.82	$157.80	$157.80
Purchase #7	$241.50	10.410%	$266.6402	$266.64	$266.65	$266.60
7 purchase totals =	$765.76		$830.0487	$830.05	$830.00	$829.90