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	$51.81	13.593%	$58.8525	$58.85	$58.85	$58.90
Purchase #2	$80.96	4.377%	$84.5036	$84.50	$84.50	$84.50
Purchase #3	$35.67	7.717%	$38.4227	$38.42	$38.40	$38.40
Purchase #4	$223.64	9.768%	$245.4852	$245.49	$245.50	$245.50
Purchase #5	$243.48	3.828%	$252.8004	$252.80	$252.80	$252.80
Purchase #6	$167.61	13.569%	$190.353	$190.35	$190.35	$190.40
Purchase #7	$174.85	12.581%	$196.8479	$196.85	$196.85	$196.80
7 purchase totals =	$978.02		$1,067.2653	$1,067.26	$1,067.25	$1,067.30