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	$193.92	13.310%	$219.7308	$219.73	$219.75	$219.70
Purchase #2	$237.29	11.605%	$264.8275	$264.83	$264.85	$264.80
Purchase #3	$168.32	6.777%	$179.727	$179.73	$179.75	$179.70
Purchase #4	$146.32	10.241%	$161.3046	$161.30	$161.30	$161.30
Purchase #5	$174.91	12.199%	$196.2473	$196.25	$196.25	$196.20
Purchase #6	$137.32	13.750%	$156.2015	$156.20	$156.20	$156.20
Purchase #7	$164.69	6.202%	$174.9041	$174.90	$174.90	$174.90
7 purchase totals =	$1,222.77		$1,352.9428	$1,352.94	$1,353.00	$1,352.80