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	$137.63	5.640%	$145.3923	$145.39	$145.40	$145.40
Purchase #2	$156.94	7.614%	$168.8894	$168.89	$168.90	$168.90
Purchase #3	$241.32	8.627%	$262.1387	$262.14	$262.15	$262.10
Purchase #4	$45.77	12.661%	$51.5649	$51.56	$51.55	$51.60
Purchase #5	$204.96	9.673%	$224.7858	$224.79	$224.80	$224.80
Purchase #6	$26.89	5.732%	$28.4313	$28.43	$28.45	$28.40
Purchase #7	$93.91	10.551%	$103.8184	$103.82	$103.80	$103.80
7 purchase totals =	$907.42		$985.0208	$985.02	$985.05	$985.00