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	$160.52	13.781%	$182.6413	$182.64	$182.65	$182.60
Purchase #2	$196.84	10.334%	$217.1814	$217.18	$217.20	$217.20
Purchase #3	$136.30	13.260%	$154.3734	$154.37	$154.35	$154.40
Purchase #4	$37.63	7.624%	$40.4989	$40.50	$40.50	$40.50
Purchase #5	$70.56	3.796%	$73.2385	$73.24	$73.25	$73.20
Purchase #6	$246.37	5.394%	$259.6592	$259.66	$259.65	$259.70
Purchase #7	$79.42	8.108%	$85.8594	$85.86	$85.85	$85.90
7 purchase totals =	$927.64		$1,013.4521	$1,013.45	$1,013.45	$1,013.50