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	$113.42	4.527%	$118.5545	$118.55	$118.55	$118.60
Purchase #2	$19.40	5.179%	$20.4047	$20.40	$20.40	$20.40
Purchase #3	$190.79	4.638%	$199.6388	$199.64	$199.65	$199.60
Purchase #4	$67.71	4.240%	$70.5809	$70.58	$70.60	$70.60
Purchase #5	$90.90	3.410%	$93.9997	$94.00	$94.00	$94.00
Purchase #6	$137.68	3.790%	$142.8981	$142.90	$142.90	$142.90
Purchase #7	$136.44	7.193%	$146.2541	$146.25	$146.25	$146.30
7 purchase totals =	$756.34		$792.3308	$792.32	$792.35	$792.40