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	$118.26	7.666%	$127.3258	$127.33	$127.35	$127.30
Purchase #2	$118.35	11.256%	$131.6715	$131.67	$131.65	$131.70
Purchase #3	$36.93	11.166%	$41.0536	$41.05	$41.05	$41.10
Purchase #4	$152.51	9.831%	$167.5033	$167.50	$167.50	$167.50
Purchase #5	$189.82	8.440%	$205.8408	$205.84	$205.85	$205.80
Purchase #6	$187.94	11.381%	$209.3295	$209.33	$209.35	$209.30
Purchase #7	$20.45	5.823%	$21.6408	$21.64	$21.65	$21.60
7 purchase totals =	$824.26		$904.3653	$904.36	$904.40	$904.30