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	$133.63	7.330%	$143.4251	$143.43	$143.45	$143.40
Purchase #2	$48.94	4.468%	$51.1266	$51.13	$51.15	$51.10
Purchase #3	$249.84	7.747%	$269.1951	$269.20	$269.20	$269.20
Purchase #4	$37.36	10.162%	$41.1565	$41.16	$41.15	$41.20
Purchase #5	$165.46	4.204%	$172.4159	$172.42	$172.40	$172.40
Purchase #6	$210.60	13.280%	$238.5677	$238.57	$238.55	$238.60
Purchase #7	$86.51	8.159%	$93.5684	$93.57	$93.55	$93.60
7 purchase totals =	$932.34		$1,009.4553	$1,009.48	$1,009.45	$1,009.50