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	$179.63	11.653%	$200.5623	$200.56	$200.55	$200.60
Purchase #2	$96.35	9.653%	$105.6507	$105.65	$105.65	$105.70
Purchase #3	$187.99	13.694%	$213.7334	$213.73	$213.75	$213.70
Purchase #4	$121.93	8.521%	$132.3197	$132.32	$132.30	$132.30
Purchase #5	$152.44	13.404%	$172.8731	$172.87	$172.85	$172.90
Purchase #6	$203.36	12.476%	$228.7312	$228.73	$228.75	$228.70
Purchase #7	$208.80	6.552%	$222.4806	$222.48	$222.50	$222.50
7 purchase totals =	$1,150.50		$1,276.3510	$1,276.34	$1,276.35	$1,276.40