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	$192.49	7.225%	$206.3974	$206.40	$206.40	$206.40
Purchase #2	$67.93	4.647%	$71.0867	$71.09	$71.10	$71.10
Purchase #3	$159.27	3.106%	$164.2169	$164.22	$164.20	$164.20
Purchase #4	$174.30	12.728%	$196.4849	$196.48	$196.50	$196.50
Purchase #5	$177.67	9.672%	$194.8542	$194.85	$194.85	$194.90
Purchase #6	$112.41	12.467%	$126.4242	$126.42	$126.40	$126.40
Purchase #7	$91.54	6.328%	$97.3327	$97.33	$97.35	$97.30
7 purchase totals =	$975.61		$1,056.7970	$1,056.79	$1,056.80	$1,056.80