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	$212.37	3.399%	$219.5885	$219.59	$219.60	$219.60
Purchase #2	$168.26	13.124%	$190.3424	$190.34	$190.35	$190.30
Purchase #3	$242.40	6.632%	$258.476	$258.48	$258.50	$258.50
Purchase #4	$77.33	4.313%	$80.6652	$80.67	$80.65	$80.70
Purchase #5	$86.41	4.542%	$90.3347	$90.33	$90.35	$90.30
Purchase #6	$94.29	6.628%	$100.5395	$100.54	$100.55	$100.50
Purchase #7	$222.73	4.157%	$231.9889	$231.99	$232.00	$232.00
7 purchase totals =	$1,103.79		$1,171.9352	$1,171.94	$1,172.00	$1,171.90