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	$236.72	11.249%	$263.3486	$263.35	$263.35	$263.30
Purchase #2	$27.38	8.762%	$29.779	$29.78	$29.80	$29.80
Purchase #3	$159.40	3.197%	$164.496	$164.50	$164.50	$164.50
Purchase #4	$48.71	13.647%	$55.3575	$55.36	$55.35	$55.40
Purchase #5	$67.64	8.747%	$73.5565	$73.56	$73.55	$73.60
Purchase #6	$248.96	12.279%	$279.5298	$279.53	$279.55	$279.50
Purchase #7	$157.86	6.124%	$167.5273	$167.53	$167.55	$167.50
7 purchase totals =	$946.67		$1,033.5947	$1,033.61	$1,033.65	$1,033.60