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	$213.52	6.716%	$227.86	$227.86	$227.85	$227.90
Purchase #2	$92.96	7.195%	$99.6485	$99.65	$99.65	$99.60
Purchase #3	$102.56	13.505%	$116.4107	$116.41	$116.40	$116.40
Purchase #4	$243.86	5.601%	$257.5186	$257.52	$257.50	$257.50
Purchase #5	$87.39	10.364%	$96.4471	$96.45	$96.45	$96.40
Purchase #6	$180.87	4.766%	$189.4903	$189.49	$189.50	$189.50
Purchase #7	$89.93	7.579%	$96.7458	$96.75	$96.75	$96.70
7 purchase totals =	$1,011.09		$1,084.1210	$1,084.13	$1,084.10	$1,084.00