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	$100.43	3.692%	$104.1379	$104.14	$104.15	$104.10
Purchase #2	$246.33	9.271%	$269.1673	$269.17	$269.15	$269.20
Purchase #3	$121.62	12.256%	$136.5257	$136.53	$136.55	$136.50
Purchase #4	$44.79	4.633%	$46.8651	$46.87	$46.85	$46.90
Purchase #5	$144.60	5.713%	$152.861	$152.86	$152.85	$152.90
Purchase #6	$114.86	7.819%	$123.8409	$123.84	$123.85	$123.80
Purchase #7	$214.69	10.562%	$237.3656	$237.37	$237.35	$237.40
7 purchase totals =	$987.32		$1,070.7635	$1,070.78	$1,070.75	$1,070.80