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	$139.55	12.365%	$156.8054	$156.81	$156.80	$156.80
Purchase #2	$241.78	6.812%	$258.2501	$258.25	$258.25	$258.30
Purchase #3	$148.56	5.314%	$156.4545	$156.45	$156.45	$156.50
Purchase #4	$183.44	8.692%	$199.3846	$199.38	$199.40	$199.40
Purchase #5	$7.33	3.580%	$7.5924	$7.59	$7.60	$7.60
Purchase #6	$105.70	4.204%	$110.1436	$110.14	$110.15	$110.10
Purchase #7	$190.47	8.544%	$206.7438	$206.74	$206.75	$206.70
7 purchase totals =	$1,016.83		$1,095.3744	$1,095.36	$1,095.40	$1,095.40