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	$61.83	9.699%	$67.8269	$67.83	$67.85	$67.80
Purchase #2	$203.65	12.340%	$228.7804	$228.78	$228.80	$228.80
Purchase #3	$222.32	6.435%	$236.6263	$236.63	$236.65	$236.60
Purchase #4	$166.79	9.612%	$182.8219	$182.82	$182.80	$182.80
Purchase #5	$140.66	8.702%	$152.9002	$152.90	$152.90	$152.90
Purchase #6	$54.52	5.660%	$57.6058	$57.61	$57.60	$57.60
Purchase #7	$168.82	3.161%	$174.1564	$174.16	$174.15	$174.20
7 purchase totals =	$1,018.59		$1,100.7179	$1,100.73	$1,100.75	$1,100.70