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	$184.69	6.466%	$196.6321	$196.63	$196.65	$196.60
Purchase #2	$167.94	12.869%	$189.5522	$189.55	$189.55	$189.60
Purchase #3	$92.33	9.777%	$101.3571	$101.36	$101.35	$101.40
Purchase #4	$6.88	3.773%	$7.1396	$7.14	$7.15	$7.10
Purchase #5	$185.52	6.392%	$197.3784	$197.38	$197.40	$197.40
Purchase #6	$172.51	4.487%	$180.2505	$180.25	$180.25	$180.30
Purchase #7	$83.25	8.686%	$90.4811	$90.48	$90.50	$90.50
7 purchase totals =	$893.12		$962.7910	$962.79	$962.85	$962.90