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	$185.89	5.826%	$196.72	$196.72	$196.70	$196.70
Purchase #2	$110.56	6.859%	$118.1433	$118.14	$118.15	$118.10
Purchase #3	$187.42	3.867%	$194.6675	$194.67	$194.65	$194.70
Purchase #4	$20.48	3.181%	$21.1315	$21.13	$21.15	$21.10
Purchase #5	$201.55	8.484%	$218.6495	$218.65	$218.65	$218.60
Purchase #6	$67.56	4.164%	$70.3732	$70.37	$70.35	$70.40
Purchase #7	$194.37	7.400%	$208.7534	$208.75	$208.75	$208.80
7 purchase totals =	$967.83		$1,028.4384	$1,028.43	$1,028.40	$1,028.40