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	$184.62	13.224%	$209.0341	$209.03	$209.05	$209.00
Purchase #2	$33.27	13.600%	$37.7947	$37.79	$37.80	$37.80
Purchase #3	$236.75	10.462%	$261.5188	$261.52	$261.50	$261.50
Purchase #4	$86.86	10.267%	$95.7779	$95.78	$95.80	$95.80
Purchase #5	$171.92	13.341%	$194.8558	$194.86	$194.85	$194.90
Purchase #6	$142.74	9.579%	$156.4131	$156.41	$156.40	$156.40
Purchase #7	$180.65	13.724%	$205.4424	$205.44	$205.45	$205.40
7 purchase totals =	$1,036.81		$1,160.8368	$1,160.83	$1,160.85	$1,160.80