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	$186.36	13.427%	$211.3826	$211.38	$211.40	$211.40
Purchase #2	$133.45	8.453%	$144.7305	$144.73	$144.75	$144.70
Purchase #3	$74.43	10.542%	$82.2764	$82.28	$82.30	$82.30
Purchase #4	$239.51	6.698%	$255.5524	$255.55	$255.55	$255.60
Purchase #5	$167.99	6.448%	$178.822	$178.82	$178.80	$178.80
Purchase #6	$76.29	13.272%	$86.4152	$86.42	$86.40	$86.40
Purchase #7	$62.64	13.436%	$71.0563	$71.06	$71.05	$71.10
7 purchase totals =	$940.67		$1,030.2354	$1,030.24	$1,030.25	$1,030.30