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	$83.61	3.843%	$86.8231	$86.82	$86.80	$86.80
Purchase #2	$119.97	12.128%	$134.52	$134.52	$134.50	$134.50
Purchase #3	$91.74	10.287%	$101.1773	$101.18	$101.20	$101.20
Purchase #4	$77.98	5.550%	$82.3079	$82.31	$82.30	$82.30
Purchase #5	$138.63	5.702%	$146.5347	$146.53	$146.55	$146.50
Purchase #6	$20.53	10.105%	$22.6046	$22.60	$22.60	$22.60
Purchase #7	$203.47	4.125%	$211.8631	$211.86	$211.85	$211.90
7 purchase totals =	$735.93		$785.8307	$785.82	$785.80	$785.80