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	$172.26	6.141%	$182.8385	$182.84	$182.85	$182.80
Purchase #2	$121.89	10.266%	$134.4032	$134.40	$134.40	$134.40
Purchase #3	$168.43	7.122%	$180.4256	$180.43	$180.45	$180.40
Purchase #4	$249.53	12.333%	$280.3045	$280.30	$280.30	$280.30
Purchase #5	$101.63	13.297%	$115.1437	$115.14	$115.15	$115.10
Purchase #6	$77.32	5.466%	$81.5463	$81.55	$81.55	$81.50
Purchase #7	$29.76	12.220%	$33.3967	$33.40	$33.40	$33.40
7 purchase totals =	$920.82		$1,008.0585	$1,008.06	$1,008.10	$1,007.90