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	$96.30	4.154%	$100.3003	$100.30	$100.30	$100.30
Purchase #2	$88.80	4.525%	$92.8182	$92.82	$92.80	$92.80
Purchase #3	$40.59	4.602%	$42.458	$42.46	$42.45	$42.50
Purchase #4	$41.40	12.116%	$46.416	$46.42	$46.40	$46.40
Purchase #5	$84.57	6.715%	$90.2489	$90.25	$90.25	$90.20
Purchase #6	$76.86	3.311%	$79.4048	$79.40	$79.40	$79.40
Purchase #7	$116.31	4.576%	$121.6323	$121.63	$121.65	$121.60
7 purchase totals =	$544.83		$573.2785	$573.28	$573.25	$573.20