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	$238.28	9.800%	$261.6314	$261.63	$261.65	$261.60
Purchase #2	$114.55	11.214%	$127.3956	$127.40	$127.40	$127.40
Purchase #3	$100.45	4.412%	$104.8819	$104.88	$104.90	$104.90
Purchase #4	$96.39	9.604%	$105.6473	$105.65	$105.65	$105.60
Purchase #5	$72.77	11.172%	$80.8999	$80.90	$80.90	$80.90
Purchase #6	$174.26	10.690%	$192.8884	$192.89	$192.90	$192.90
Purchase #7	$249.65	7.604%	$268.6334	$268.63	$268.65	$268.60
7 purchase totals =	$1,046.35		$1,141.9779	$1,141.98	$1,142.05	$1,141.90