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	$221.94	13.280%	$251.4136	$251.41	$251.40	$251.40
Purchase #2	$179.76	9.206%	$196.3087	$196.31	$196.30	$196.30
Purchase #3	$47.39	6.139%	$50.2993	$50.30	$50.30	$50.30
Purchase #4	$208.64	13.267%	$236.3203	$236.32	$236.30	$236.30
Purchase #5	$89.88	8.241%	$97.287	$97.29	$97.30	$97.30
Purchase #6	$140.84	7.801%	$151.8269	$151.83	$151.85	$151.80
Purchase #7	$214.83	4.757%	$225.0495	$225.05	$225.05	$225.00
7 purchase totals =	$1,103.28		$1,208.5053	$1,208.51	$1,208.50	$1,208.40