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	$83.38	10.352%	$92.0115	$92.01	$92.00	$92.00
Purchase #2	$39.71	7.229%	$42.5806	$42.58	$42.60	$42.60
Purchase #3	$62.45	5.482%	$65.8735	$65.87	$65.85	$65.90
Purchase #4	$215.38	6.261%	$228.8649	$228.86	$228.85	$228.90
Purchase #5	$180.63	4.736%	$189.1846	$189.18	$189.20	$189.20
Purchase #6	$54.56	4.136%	$56.8166	$56.82	$56.80	$56.80
Purchase #7	$151.79	4.229%	$158.2092	$158.21	$158.20	$158.20
7 purchase totals =	$787.90		$833.5409	$833.53	$833.50	$833.60