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	$194.93	12.226%	$218.7621	$218.76	$218.75	$218.80
Purchase #2	$41.83	9.831%	$45.9423	$45.94	$45.95	$45.90
Purchase #3	$156.85	12.613%	$176.6335	$176.63	$176.65	$176.60
Purchase #4	$82.55	4.789%	$86.5033	$86.50	$86.50	$86.50
Purchase #5	$217.73	6.152%	$231.1247	$231.12	$231.10	$231.10
Purchase #6	$124.46	4.732%	$130.3494	$130.35	$130.35	$130.30
Purchase #7	$151.82	9.631%	$166.4418	$166.44	$166.45	$166.40
7 purchase totals =	$970.17		$1,055.7571	$1,055.74	$1,055.75	$1,055.60