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	$103.62	7.579%	$111.4734	$111.47	$111.45	$111.50
Purchase #2	$36.58	9.558%	$40.0763	$40.08	$40.10	$40.10
Purchase #3	$174.72	10.822%	$193.6282	$193.63	$193.65	$193.60
Purchase #4	$116.59	13.133%	$131.9018	$131.90	$131.90	$131.90
Purchase #5	$56.33	5.727%	$59.556	$59.56	$59.55	$59.60
Purchase #6	$106.46	10.240%	$117.3615	$117.36	$117.35	$117.40
Purchase #7	$16.49	5.814%	$17.4487	$17.45	$17.45	$17.40
7 purchase totals =	$610.79		$671.4459	$671.45	$671.45	$671.50