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	$126.25	11.389%	$140.6286	$140.63	$140.65	$140.60
Purchase #2	$68.96	5.328%	$72.6342	$72.63	$72.65	$72.60
Purchase #3	$151.87	10.707%	$168.1307	$168.13	$168.15	$168.10
Purchase #4	$202.55	8.834%	$220.4433	$220.44	$220.45	$220.40
Purchase #5	$220.53	9.809%	$242.1618	$242.16	$242.15	$242.20
Purchase #6	$90.69	10.519%	$100.2297	$100.23	$100.25	$100.20
Purchase #7	$219.37	3.694%	$227.4735	$227.47	$227.45	$227.50
7 purchase totals =	$1,080.22		$1,171.7018	$1,171.69	$1,171.75	$1,171.60