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	$162.91	11.290%	$181.3025	$181.30	$181.30	$181.30
Purchase #2	$234.48	6.163%	$248.931	$248.93	$248.95	$248.90
Purchase #3	$180.88	5.643%	$191.0871	$191.09	$191.10	$191.10
Purchase #4	$237.81	7.561%	$255.7908	$255.79	$255.80	$255.80
Purchase #5	$177.98	4.170%	$185.4018	$185.40	$185.40	$185.40
Purchase #6	$19.82	7.792%	$21.3644	$21.36	$21.35	$21.40
Purchase #7	$11.79	6.504%	$12.5568	$12.56	$12.55	$12.60
7 purchase totals =	$1,025.67		$1,096.4344	$1,096.43	$1,096.45	$1,096.50