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	$222.65	6.837%	$237.8726	$237.87	$237.85	$237.90
Purchase #2	$53.99	9.376%	$59.0521	$59.05	$59.05	$59.10
Purchase #3	$240.34	9.390%	$262.9079	$262.91	$262.90	$262.90
Purchase #4	$108.34	13.729%	$123.214	$123.21	$123.20	$123.20
Purchase #5	$220.95	10.393%	$243.9133	$243.91	$243.90	$243.90
Purchase #6	$154.35	6.789%	$164.8288	$164.83	$164.85	$164.80
Purchase #7	$163.88	9.322%	$179.1569	$179.16	$179.15	$179.20
7 purchase totals =	$1,164.50		$1,270.9456	$1,270.94	$1,270.90	$1,271.00