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	$198.29	5.791%	$209.773	$209.77	$209.75	$209.80
Purchase #2	$222.49	6.667%	$237.3234	$237.32	$237.30	$237.30
Purchase #3	$85.68	3.387%	$88.582	$88.58	$88.60	$88.60
Purchase #4	$57.31	4.379%	$59.8196	$59.82	$59.80	$59.80
Purchase #5	$212.94	11.419%	$237.2556	$237.26	$237.25	$237.30
Purchase #6	$148.81	10.505%	$164.4425	$164.44	$164.45	$164.40
Purchase #7	$75.63	10.318%	$83.4335	$83.43	$83.45	$83.40
7 purchase totals =	$1,001.15		$1,080.6296	$1,080.62	$1,080.60	$1,080.60