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	$90.36	5.607%	$95.4265	$95.43	$95.45	$95.40
Purchase #2	$42.91	13.668%	$48.7749	$48.77	$48.75	$48.80
Purchase #3	$160.81	3.722%	$166.7953	$166.80	$166.80	$166.80
Purchase #4	$189.52	12.820%	$213.8165	$213.82	$213.80	$213.80
Purchase #5	$126.39	8.211%	$136.7679	$136.77	$136.75	$136.80
Purchase #6	$206.34	7.734%	$222.2983	$222.30	$222.30	$222.30
Purchase #7	$239.64	6.648%	$255.5713	$255.57	$255.55	$255.60
7 purchase totals =	$1,055.97		$1,139.4507	$1,139.46	$1,139.40	$1,139.50