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	$93.27	3.866%	$96.8758	$96.88	$96.90	$96.90
Purchase #2	$90.82	6.173%	$96.4263	$96.43	$96.45	$96.40
Purchase #3	$244.27	12.143%	$273.9317	$273.93	$273.95	$273.90
Purchase #4	$88.84	3.422%	$91.8801	$91.88	$91.90	$91.90
Purchase #5	$242.37	12.170%	$271.8664	$271.87	$271.85	$271.90
Purchase #6	$137.27	5.151%	$144.3408	$144.34	$144.35	$144.30
Purchase #7	$167.80	12.337%	$188.5015	$188.50	$188.50	$188.50
7 purchase totals =	$1,064.64		$1,163.8226	$1,163.83	$1,163.90	$1,163.80