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	$43.69	4.210%	$45.5293	$45.53	$45.55	$45.50
Purchase #2	$127.45	11.780%	$142.4636	$142.46	$142.45	$142.50
Purchase #3	$174.50	7.141%	$186.961	$186.96	$186.95	$187.00
Purchase #4	$216.85	4.157%	$225.8645	$225.86	$225.85	$225.90
Purchase #5	$190.47	8.660%	$206.9647	$206.96	$206.95	$207.00
Purchase #6	$73.26	4.577%	$76.6131	$76.61	$76.60	$76.60
Purchase #7	$184.86	12.469%	$207.9102	$207.91	$207.90	$207.90
7 purchase totals =	$1,011.08		$1,092.3064	$1,092.29	$1,092.25	$1,092.40