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	$92.98	7.449%	$99.9061	$99.91	$99.90	$99.90
Purchase #2	$28.79	4.702%	$30.1437	$30.14	$30.15	$30.10
Purchase #3	$163.82	9.822%	$179.9104	$179.91	$179.90	$179.90
Purchase #4	$97.87	7.508%	$105.2181	$105.22	$105.20	$105.20
Purchase #5	$143.25	12.625%	$161.3353	$161.34	$161.35	$161.30
Purchase #6	$179.34	9.422%	$196.2374	$196.24	$196.25	$196.20
Purchase #7	$220.70	7.555%	$237.3739	$237.37	$237.35	$237.40
7 purchase totals =	$926.75		$1,010.1249	$1,010.13	$1,010.10	$1,010.00