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	$89.37	7.150%	$95.76	$95.76	$95.75	$95.80
Purchase #2	$105.59	6.458%	$112.409	$112.41	$112.40	$112.40
Purchase #3	$72.45	13.309%	$82.0924	$82.09	$82.10	$82.10
Purchase #4	$12.54	12.379%	$14.0923	$14.09	$14.10	$14.10
Purchase #5	$53.91	9.490%	$59.0261	$59.03	$59.05	$59.00
Purchase #6	$166.67	4.630%	$174.3868	$174.39	$174.40	$174.40
Purchase #7	$114.46	10.706%	$126.7141	$126.71	$126.70	$126.70
7 purchase totals =	$614.99		$664.4807	$664.48	$664.50	$664.50