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	$99.55	6.548%	$106.0685	$106.07	$106.05	$106.10
Purchase #2	$108.85	13.351%	$123.3826	$123.38	$123.40	$123.40
Purchase #3	$124.90	5.361%	$131.5959	$131.60	$131.60	$131.60
Purchase #4	$192.89	10.871%	$213.8591	$213.86	$213.85	$213.90
Purchase #5	$55.94	12.330%	$62.8374	$62.84	$62.85	$62.80
Purchase #6	$197.33	4.731%	$206.6657	$206.67	$206.65	$206.70
Purchase #7	$156.87	5.241%	$165.0916	$165.09	$165.10	$165.10
7 purchase totals =	$936.33		$1,009.5008	$1,009.51	$1,009.50	$1,009.60