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	$122.36	6.179%	$129.9206	$129.92	$129.90	$129.90
Purchase #2	$81.96	5.566%	$86.5219	$86.52	$86.50	$86.50
Purchase #3	$41.32	11.572%	$46.1016	$46.10	$46.10	$46.10
Purchase #4	$241.47	11.571%	$269.4105	$269.41	$269.40	$269.40
Purchase #5	$239.86	7.814%	$258.6027	$258.60	$258.60	$258.60
Purchase #6	$185.93	5.445%	$196.0539	$196.05	$196.05	$196.10
Purchase #7	$248.92	13.447%	$282.3923	$282.39	$282.40	$282.40
7 purchase totals =	$1,161.82		$1,269.0035	$1,268.99	$1,268.95	$1,269.00