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	$207.47	7.651%	$223.3435	$223.34	$223.35	$223.30
Purchase #2	$57.46	3.715%	$59.5946	$59.59	$59.60	$59.60
Purchase #3	$174.87	6.700%	$186.5863	$186.59	$186.60	$186.60
Purchase #4	$12.99	11.324%	$14.461	$14.46	$14.45	$14.50
Purchase #5	$122.88	11.688%	$137.2422	$137.24	$137.25	$137.20
Purchase #6	$168.56	4.445%	$176.0525	$176.05	$176.05	$176.10
Purchase #7	$182.83	9.179%	$199.612	$199.61	$199.60	$199.60
7 purchase totals =	$927.06		$996.8921	$996.88	$996.90	$996.90