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	$86.86	6.454%	$92.4659	$92.47	$92.45	$92.50
Purchase #2	$162.76	9.561%	$178.3215	$178.32	$178.30	$178.30
Purchase #3	$32.46	12.605%	$36.5516	$36.55	$36.55	$36.60
Purchase #4	$36.59	3.457%	$37.8549	$37.85	$37.85	$37.90
Purchase #5	$232.52	3.263%	$240.1071	$240.11	$240.10	$240.10
Purchase #6	$191.64	8.706%	$208.3242	$208.32	$208.30	$208.30
Purchase #7	$218.68	8.760%	$237.8364	$237.84	$237.85	$237.80
7 purchase totals =	$961.51		$1,031.4616	$1,031.46	$1,031.40	$1,031.50