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	$56.35	10.618%	$62.3332	$62.33	$62.35	$62.30
Purchase #2	$162.41	5.687%	$171.6463	$171.65	$171.65	$171.60
Purchase #3	$193.42	3.295%	$199.7932	$199.79	$199.80	$199.80
Purchase #4	$139.54	12.215%	$156.5848	$156.58	$156.60	$156.60
Purchase #5	$17.75	4.629%	$18.5716	$18.57	$18.55	$18.60
Purchase #6	$112.40	6.415%	$119.6105	$119.61	$119.60	$119.60
Purchase #7	$71.40	13.183%	$80.8127	$80.81	$80.80	$80.80
7 purchase totals =	$753.27		$809.3523	$809.34	$809.35	$809.30