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	$10.89	5.199%	$11.4562	$11.46	$11.45	$11.50
Purchase #2	$60.28	6.328%	$64.0945	$64.09	$64.10	$64.10
Purchase #3	$240.96	5.201%	$253.4923	$253.49	$253.50	$253.50
Purchase #4	$180.27	11.582%	$201.1489	$201.15	$201.15	$201.10
Purchase #5	$156.47	10.164%	$172.3736	$172.37	$172.35	$172.40
Purchase #6	$63.60	12.438%	$71.5106	$71.51	$71.50	$71.50
Purchase #7	$228.89	6.660%	$244.1341	$244.13	$244.15	$244.10
7 purchase totals =	$941.36		$1,018.2102	$1,018.20	$1,018.20	$1,018.20