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	$80.35	7.841%	$86.6502	$86.65	$86.65	$86.70
Purchase #2	$100.32	9.184%	$109.5334	$109.53	$109.55	$109.50
Purchase #3	$212.72	6.544%	$226.6404	$226.64	$226.65	$226.60
Purchase #4	$129.75	11.613%	$144.8179	$144.82	$144.80	$144.80
Purchase #5	$200.74	9.654%	$220.1194	$220.12	$220.10	$220.10
Purchase #6	$188.91	4.166%	$196.78	$196.78	$196.80	$196.80
Purchase #7	$103.94	9.748%	$114.0721	$114.07	$114.05	$114.10
7 purchase totals =	$1,016.73		$1,098.6134	$1,098.61	$1,098.60	$1,098.60