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	$27.63	4.160%	$28.7794	$28.78	$28.80	$28.80
Purchase #2	$87.85	4.599%	$91.8902	$91.89	$91.90	$91.90
Purchase #3	$55.96	10.538%	$61.8571	$61.86	$61.85	$61.90
Purchase #4	$139.49	9.472%	$152.7025	$152.70	$152.70	$152.70
Purchase #5	$53.61	5.870%	$56.7569	$56.76	$56.75	$56.80
Purchase #6	$161.34	12.237%	$181.0832	$181.08	$181.10	$181.10
Purchase #7	$200.35	12.103%	$224.5984	$224.60	$224.60	$224.60
7 purchase totals =	$726.23		$797.6677	$797.67	$797.70	$797.80