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	$242.38	13.806%	$275.843	$275.84	$275.85	$275.80
Purchase #2	$43.43	4.754%	$45.4947	$45.49	$45.50	$45.50
Purchase #3	$69.39	4.279%	$72.3592	$72.36	$72.35	$72.40
Purchase #4	$171.39	7.678%	$184.5493	$184.55	$184.55	$184.50
Purchase #5	$156.52	3.378%	$161.8072	$161.81	$161.80	$161.80
Purchase #6	$127.74	13.460%	$144.9338	$144.93	$144.95	$144.90
Purchase #7	$164.49	9.774%	$180.5673	$180.57	$180.55	$180.60
7 purchase totals =	$975.34		$1,065.5545	$1,065.55	$1,065.55	$1,065.50