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	$11.27	12.293%	$12.6554	$12.66	$12.65	$12.70
Purchase #2	$185.34	6.256%	$196.9349	$196.93	$196.95	$196.90
Purchase #3	$107.35	5.373%	$113.1179	$113.12	$113.10	$113.10
Purchase #4	$134.77	4.822%	$141.2686	$141.27	$141.25	$141.30
Purchase #5	$154.30	11.368%	$171.8408	$171.84	$171.85	$171.80
Purchase #6	$229.86	4.650%	$240.5485	$240.55	$240.55	$240.50
Purchase #7	$224.59	7.310%	$241.0075	$241.01	$241.00	$241.00
7 purchase totals =	$1,047.48		$1,117.3736	$1,117.38	$1,117.35	$1,117.30